@capnomo 

You may have 2 options:

1. If you prefer to use QBD 2018 Enterprise, you will have to migrate your data with a 3rd party tool.

https://transactionpro.grsm.io/qbd

2. If you are concerned about the subscription license, you can still purchase a one-time license for QBD 2021 Pro/Premier. You can purchase a 3rd party service to downgrade your Enterprise file. Contact us in private for details.