Move ACF fields into repeater

//add_action('wp_head', 'update_meta_values');
function update_meta_values() {

	/*
	 * Takes a set of fields and resets them as part of a repeater
	 * To start, create a new repeater field and enter the slug in $new_repeater
	 * Find the fields you would like to move in wp_posts and set the post_parent to the new repeater's ID
	 */

	// Slug of the new repeater
	$new_repeater = 'repeater_field';
	
	// Set the fields you would like to move's slugs in $rows
	$rows = array(
		'foo',
		'bar'
	);

	// Query the effected posts
	$args = array(
		'post_type' => array( 'cpt_post_type' ),
		'posts_per_page' => -1
	);

	$posts = get_posts($args);

	foreach ($posts as $post) {

		// Update Meta Fields
		$id = $post->ID;
		$meta = get_post_meta( $id );
		unset($updated);

		// Loop each posts Meta values
		foreach ( $meta as $key => $value ) {
			
			// Loop the possible fields
			foreach ( $rows as $row ) {
				
				//Check if field name is in meta value
				if ( strpos( $key, $row ) !== false ) {

					// Grab the value's name, prepend it with the repeater name.
					$new_post_meta = str_replace( $row, $new_repeater . '_0_' . $row , $key );
					
					// Add new meta
					update_post_meta( $id, $new_post_meta, $value[0] );
					
					// Delete old meta
					delete_post_meta( $id, $key );
					$updated = true;
					break;
				}
			}
		}

		// If this post has repeater rows, mark it with 1
		if ($updated) {
			update_post_meta( $id, 'resource_list', 1 );
			update_post_meta( $id, '_resource_list', 'field_574ee7028384d' );
		}

	}
}

Thank you for this hack

I found how to do it directly in the back office
First you have to add a subfield to the repeater field and save
Then drag the desired field and drop it in the sub-fields block of the repeater

@gthayer Thank you for this. I ended up taking your code and running with it for a plugin/WP CLI command: https://github.com/kodie/migrate-acf-field-data-to-repeater