With Shopware 5, a temporary order is created when a customer enters the checkout process. The plugin transfers this temporary order (the shopping cart) to Mailchimp and deletes this data once the temporary order has been converted into a real order.
The easiest way to see the transferred shopping carts is to query the Mailchimp API directly:
https://mailchimp.com/developer/marketing/api/ecommerce-carts/
Another alternative would be to go to your shop's checkout yourself and then look at the queue entries in the “Advanced” tab. Here you will find an entry of type TYPE_ADD_TEMPORARY, provided that you have enabled the transfer of temporary shopping carts in the plugin settings.
