Woocommerce Memberships Extract Memberships ID

I would like to add the membership ID in the “new order” email sent automatically from woocommerce.
This is the code in the email_header:

$orderID = explode("#", $email_heading); 
                            $order = new WC_Order($orderID[1]);
                            $user = get_user_by( 'email', $order->get_billing_email());
                            $memberships = wc_memberships_get_user_active_memberships($user->ID);
                            foreach ( $memberships as $v ) {
                                $member = (array) $v;
                            }
                            $orderN = explode('_', $member['plan']->name);
                            $ordine = $orderN[1];
                            $output = 'Codice cliente: '.$ordine.'<br>';

I have tried several different things according to woocommerce memberships documentation. However I can’t display the memberships user id.
The problem seems to be at wc_memberships_get_user_active_memberships($user->ID);, but I can’t be sure as everything I have tried displayed blank.

Any help on that? thank you!