How to convert maven project to gradle?

I have a project (spring + angular) built on maven. And I would like to replace the automation tool using gradle.

The project contains 3 pom.xml files. The structure looks like this.

-MainApp
 -pom.xml
 -- spring (contains pom.xml)
 -- angular (contains pom.xml)

In summary, the application's root folder contains a pom.xml file, and it also contains 2 folders angular and spring, which have a pom.xml file in their projects.

And I don't know much about how to do it, because some pom.xml files contain a reference to other pom.xml files. How can I carry out this process?

Below I paste the pom.xml files

Angular

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <parent>
        <groupId>com.javappa</groupId>
        <artifactId>mainapp</artifactId>
        <version>1.0.0</version>
    </parent>

    <artifactId>angular</artifactId>
    <packaging>jar</packaging>

    <build>
        <plugins>
            <plugin>
                <artifactId>maven-clean-plugin</artifactId>
                <version>3.1.0</version>
                <configuration>
                    <filesets>
                        <fileset>
                            <directory>dist</directory>
                        </fileset>
                    </filesets>
                </configuration>
            </plugin>
            <plugin>
                <groupId>com.github.eirslett</groupId>
                <artifactId>frontend-maven-plugin</artifactId>
                <version>1.11.2</version>

                <executions>
                    <execution>
                        <id>Install Node and NPM</id>
                        <goals>
                            <goal>install-node-and-npm</goal>
                        </goals>
                        <configuration>
                            <nodeVersion>v14.16.0</nodeVersion>
                        </configuration>
                    </execution>

                    <execution>
                        <id>npm install quill@1.3.7</id>
                        <goals>
                            <goal>npm</goal>
                        </goals>
                        <configuration>
                            <arguments>install quill@1.3.7</arguments>
                        </configuration>
                    </execution>
                    <execution>
                        <id>npm install</id>
                        <goals>
                            <goal>npm</goal>
                        </goals>
                    </execution>
                    <execution>
                        <id>npm run build</id>
                        <goals>
                            <goal>npm</goal>
                        </goals>
                        <configuration>
                            <arguments>run build --prod</arguments>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
</project>

Spring Boot

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    
    <parent> 
        <groupId>com.javappa</groupId> 
        <artifactId>mainapp</artifactId> 
        <version>1.0.0</version> 
        <relativePath>../pom.xml</relativePath>
    </parent>   
    
    <artifactId>spring-boot</artifactId>    

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.target>1.8</maven.compiler.target>
        <start-class>com.javappa.startappa.mainapp.Application</start-class>
    </properties>

    <dependencies>

        <dependency>
            <groupId>com.javappa</groupId>
            <artifactId>angular</artifactId>
            <version>1.0.0</version>
            <type>jar</type>
        </dependency>

        <dependency>
            <groupId>org.postgresql</groupId>
            <artifactId>postgresql</artifactId>
            <version>42.5.0</version>
        </dependency>


        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>

        <dependency>
            <groupId>commons-io</groupId>
            <artifactId>commons-io</artifactId>
            <version>2.4</version>
        </dependency>

        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-lang3</artifactId>
            <version>3.0</version>
        </dependency>
        
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-mail</artifactId>
        </dependency>
        
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-security</artifactId>
        </dependency>
        
        <dependency>
            <groupId>com.fasterxml.jackson.datatype</groupId>
            <artifactId>jackson-datatype-jsr310</artifactId>
        </dependency>
        
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-validation</artifactId>
        </dependency>

        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.22</version>
            <scope>provided</scope>
        </dependency>

    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>15</source>
                    <target>15</target>
                </configuration>
            </plugin>           
            <plugin> 
                <groupId>org.springframework.boot</groupId> 
                <artifactId>spring-boot-maven-plugin</artifactId> 
                <version>2.4.3</version> 
                <configuration> 
                    <mainClass>com.javappa.startappa.mainapp.Application</mainClass>
                </configuration> 
                <executions> 
                    <execution> 
                        <goals> 
                            <goal>repackage</goal> 
                        </goals> 
                    </execution> 
                </executions> 
            </plugin> 
            <plugin> 
                <groupId>org.apache.maven.plugins</groupId> 
                <artifactId>maven-dependency-plugin</artifactId> 
                <version>3.1.2</version> 
                <executions> 
                    <execution> 
                        <id>merge</id> 
                        <phase>initialize</phase> 
                        <goals> 
                            <goal>unpack</goal> 
                        </goals> 
                        <configuration> 
                            <artifactItems> 
                                <artifactItem> 
                                    <groupId>com.javappa</groupId> 
                                    <artifactId>angular</artifactId> 
                                    <type>jar</type> 
                                    <overWrite>true</overWrite> 
                                    <outputDirectory>${project.build.directory}/classes/static</outputDirectory> 
                                </artifactItem> 
                            </artifactItems> 
                        </configuration> 
                    </execution> 
                </executions> 
            </plugin>           

        </plugins>
    
    </build>

</project>

MainApp

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.javappa</groupId>
    <artifactId>mainApp</artifactId>
    <version>1.0.0</version>
    <name>MainApp</name>
    <description>MainApp</description>  
    <packaging>pom</packaging>  
    
    <parent> 
        <groupId>org.springframework.boot</groupId> 
        <artifactId>spring-boot-starter-parent</artifactId> 
        <version>2.7.3</version>
    </parent> 
    <modules> 
        <module>angular</module> 
        <module>spring-boot</module> 
    </modules> 


</project>