Siab is correct. A QBB file is a backup file type specific to QuickBooks Desktop.
To help you retrieve your data, could you please tell us when you canceled your QuickBooks Self-Employed (QBSE) subscription?
Your data is kept on our servers for one year from the cancellation date. If you are still within that 12-month period, you can resubscribe now to regain full access to your account. We strongly recommend doing so immediately to export all your data for backup and record-keeping purposes.
However, if the cancellation occurred more than one year ago, all your data will have been permanently deleted from our system, and we will not be able to retrieve it.
Please don't hesitate to reach out if you still need further assistance.