(Multisite) Customize WooCommerce order number by adding a prefix based on the current blog ID

functions.php

<?php

/**
 * // functions.php
 * Customize order number by adding a prefix based on the current blog ID
 */
add_filter('woocommerce_order_number', 'multisite_change_woocommerce_order_number', 1, 2);
function multisite_change_woocommerce_order_number($order_id, $order) {
    $blog_id = get_current_blog_id();

    switch ($blog_id) {
        case 1:
            $prefix = 'PREFIX1-';
            break;
        case 2:
            $prefix = 'PREFIX2-';
            break;
        case 3:
            $prefix = 'PREFIX3-';
            break;
        default:
            $prefix = 'DEFAULT_PREFIX-';
    }

    return $prefix . $order->get_id();
}