How to fix? "ERROR: : Could not find any version that matches com.android.support:appcompat-v7:29.+."

I import a project which is generated by unity to android studio. I have an issue in build.gradle.

I install Android Support Repository also but problem is as it is. These three errors at Sync phase

"ERROR: Unable to resolve dependency for ':@debug/compileClasspath': Could not find any version that matches com.android.support:appcompat-v7:29.+.
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Affected Modules: AR

ERROR: Unable to resolve dependency for ':@debugAndroidTest/compileClasspath': Could not find any version that matches com.android.support:appcompat-v7:29.+.
Show Details
Affected Modules: AR

ERROR: Unable to resolve dependency for ':@debugUnitTest/compileClasspath': Could not find any version that matches com.android.support:appcompat-v7:29.+.
Show Details
Affected Modules: AR"

Error at build output

Could not find any version that matches com.android.support:appcompat-v7:29.+.
Versions that do not match:
  - 28.0.0
  - 28.0.0-rc02
  - 28.0.0-rc01
  - 28.0.0-beta01
  - 28.0.0-alpha3
  - + 50 more
Required by:
    project :

Please install the Android Support Repository from the Android SDK Manager.
Open Android SDK Manager

Code of build.gradle.

-->>>>


allprojects {

    repositories {
        google()
        jcenter()
        flatDir {
            dirs 'libs'
        }
    }
}



android {
    compileSdkVersion 29
    buildToolsVersion '29.0.0'

    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }

dependencies
 {

    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation(name: 'UnityChannel', ext: 'aar')

    implementation(name: 'VuforiaWrapper', ext: 'aar')
    implementation 'com.android.support:appcompat-v7:29.+'
    implementation 'com.android.support.constraint:constraint-layout:1.1.3'
}

    defaultConfig {
        minSdkVersion 16
        targetSdkVersion 29
        applicationId 'com.hj.ar'
        ndk {
            abiFilters 'armeabi-v7a', 'x86'
        }
        versionCode 1
        versionName '1.0'
    }