I need someone to guide me very urgently!

I use WordPress with Woodmart theme and I want automatic orders to be completed.
I installed the codesnippets plugin and copied the following code from the codesnippet website:

But the order that was previously Processing is not completed!
What should I put the payment method where it says “Change the Payment Method” ?

Thanks for your help

Autocompleted WooCommerce order based on the payment method “Moneris Gateway”

add_action('woocommerce_order_status_changed', 'ts_auto_complete_by_payment_method');
 function ts_auto_complete_by_payment_method($order_id)
{
 
  if ( ! $order_id ) {
        return;
   }
  global $product;
  $order = wc_get_order( $order_id );
 
  if ($order->data['status'] == 'processing') {
        $payment_method=$order->get_payment_method();
        if ($payment_method!="cod") // Change the Payment Method
        {
            $order->update_status( 'completed' );
        }

  }

}