How to get HikaSerial number in a custom plugin

-- HikaShop version -- : 5.1.0
-- Joomla version -- : 4.4.5
-- PHP version -- : 8.2.20-nmm1

We create a custom plugin for the HikaShop. The plugin uses the onAfterOrderUpdate to take the placed order and forward the data to a CRM system. Some products have a HikaSerial randomgen package asigned. In the custom plugin I need to get the generated serialnumbers. Is there a direct way to get these numbers from the $order object? If not, is there a other smooth way or do I have to access the db directly?

Obviously my plugin come first. The $order->order_serials is empty

    [order_serials] => stdClass Object
        (
            [packs] => Array
                (
                )

            [serials] => Array
                (
                )