How to call my insert, delete, and search functions that I have created in C++

So, I have the below code where I created functions to insert, delete, and search numbers in a binary search tree.

My functions look one (as far as I know), but when I try to call my insert function, it tells me "Use of undeclared identifier "insert"".

I'm not sure what's going on or where I'm messing up here, but I ned it to be able to add a list of numbers (3,1,5,7,9,2), delete to of those, then search for a number.

I'm currently stuck and could use another set of eyes to help me catch what I'm missing, thanks!

#include <iostream>
#include <cstddef>
 
using std::cout;
using std::endl;
 
class Node {
public:
    int value;
    Node* left;       // left child
    Node* right;      // right child
    Node* p;          // parent
    Node(int data) {
        value = data;
        left = NULL;
        right = NULL;
        p = NULL;
    }
    ~Node() {
    }
    int d() {
        return value;
    }
    void print() {
        std::cout << value << std::endl;
    }
};
 
void insert(Node* insert_node, Node* tree_root) {
    if (insert_node->d() < tree_root->d()) {
        if (tree_root->left == NULL) {
            tree_root->left = insert_node;
            insert_node->p = tree_root;
        }
        else {
            insert(insert_node, tree_root->left);
        }
    }
    else {
        if (tree_root->right == NULL) {
            tree_root->right = insert_node;
            insert_node->p = tree_root;
        }
        else {
            insert(insert_node, tree_root->right);
        }
    }
}
 
void delete_node(int value, Node* tree_root) {
    if (value < tree_root->d()) {
        if (tree_root->left == NULL) {
            return;
        }
        else {
            delete_node(value, tree_root->left);
        }
    }
    else if (value > tree_root->d()) {
        if (tree_root->right == NULL) {
            return;
        }
        else {
            delete_node(value, tree_root->right);
        }
    }
    else {
        if (tree_root->left == NULL && tree_root->right == NULL) {
            if (tree_root->p->left == tree_root) {
                tree_root->p->left = NULL;
            }
            else {
                tree_root->p->right = NULL;
            }
            delete tree_root;
        }
        else if (tree_root->left == NULL) {
            if (tree_root->p->left == tree_root) {
                tree_root->p->left = tree_root->right;
            }
            else {
                tree_root->p->right = tree_root->right;
            }
            delete tree_root;
        }
        else if (tree_root->right == NULL) {
            if (tree_root->p->left == tree_root) {
                tree_root->p->left = tree_root->left;
            }
            else {
                tree_root->p->right = tree_root->left;
            }
            delete tree_root;
        }
        else {
            Node* temp = tree_root->right;
            while (temp->left != NULL) {
                temp = temp->left;
            }
            tree_root->value = temp->value;
            delete_node(temp->value, tree_root->right);
        }
    }
}
 
Node* search(int value, Node* tree_root) {
    if (value < tree_root->d()) {
        if (tree_root->left == NULL) {
            return NULL;
        }
        else {
            return search(value, tree_root->left);
        }
    }
    else if (value > tree_root->d()) {
        if (tree_root->right == NULL) {
            return NULL;
        }
        else {
            return search(value, tree_root->right);
        }
    }
    else {
        return tree_root;
    }
}
int main(int argc, const char* argv[])
{
    //USE THIS TO TEST INSERT FUNCTION
    insert(2);       //ERROR MESSAGE HERE
    insert(1);       // ""     ""      ""
    Insert(4);       // ""     ""      ""
    Insert(5);       // ""     ""      ""
    Insert(9);       // ""     ""      ""
    Insert(3);       // ""     ""      ""
    Insert(6);       // ""     ""      ""
    Insert(7);       // ""     ""      ""
    Insert(10);      // ""     ""      ""
    Insert(12);      // ""     ""      ""
    Insert(11);      // ""     ""      ""
    Insert(4);       // ""     ""      ""
    
 
    //PRINT TREE IN ORDER
    PrintTree(tree_root);
    return 0;