That's a very old Acymailing version you're using. You need to update to the latest v5 before you can migrate your data to version 6.
If you have a valid Essantial or Enterprise subscription you can download the latest v5 from your account on https://www.acymailing.com/account/license/. After that you can migrate your data to v6.
Otherwise the best way is to manually export your users, lists and templates and import them manually in v6. Although I would recommend to recreate your templates in the new v6 drag & drop editor.