As you may be aware, WooCommerce utilizes the “order ID” (which corresponds to the ID of the order post in the database) as the order number. This order number is displayed in various places such as the “WooCommerce” > “Orders” table, the order “quick view” window, the single order page, and the customer’s My Account page under the “Order” column.

However, if you require adding a prefix or a suffix to this order number to align with your business or invoice specifications, you can implement the following solution:

function fixelar_order_number_prefix( $order_id, $order ) {
   return 'Your-prefix-' . $order_id;
add_filter( 'woocommerce_order_number', 'fixelar_order_number_prefix', 9999, 2 );