How to add suffix to parent order in woocommerce?

add_filter( 'woocommerce_order_number', 'change_woocommerce_order_number' );
function change_woocommerce_order_number( $order_id ) {
	 if(is_admin()){
		 $order = wc_get_order( $order_id );
		 $parent_id = $order->get_parent_id();

		 if ( $parent_id == 0 ) {
			$order_id = 'P_'. $order_id;
		 }
		 return $order_id;
	}
	else
	{
		return $order_id;
	}
}