A PHP script as a starting point to convert old WP meta fields to ACF meta fields. Add this to theme's functions.php file.

convert-wordpress-meta-fields.php

/*
 * Use this script as a starting point to convert old WP meta fields to ACF meta fields.
 * Add ?convert_meta to the URL and load any page in backend.
 * You should edit the script, and only run it once.
 */
function custom_convert_meta_to_acf()
{
    // Abort if no query param in URL
    if(! isset($_GET["convert_meta"])) {
        return;
    }

    // Get all pages/posts/cpts
    $args = array(
        'post_type'        => 'any',
    	'posts_per_page'   => -1,
    );
    $posts = get_posts($args);
    
    $output = [];
    
    foreach($posts as $post) {        
        
        // Update selected meta fields
        // See: https://www.advancedcustomfields.com/resources/update_field/
        if($post->_custom_credits) {
            update_field("field_60cbeab35135e", $post->_custom_credits, $post->ID);            
        }

        if($post->_custom_video_url) {
            update_field("field_60cbeabc5135f", $post->_custom_video_url, $post->ID);            
        }
        
        $output[] = $post->ID;
    }
    
    var_dump("These posts were updated:", $output);

}
//add_action("admin_init", "custom_convert_meta_to_acf");