At this time, being able to import a QBB file directly into QuickBooks Online isn't available. The QBB is the file extension for a backup file format used by QuickBooks Desktop. That said, you'll need a QuickBooks Desktop version to restore this backup company and have it imported in QBO afterward.
You can use our trial links to open the backup. Once done, you may now start restoring the back up then import it. I've attached here the steps that you're going to follow so you can accomplish these processes:
Once you have converted your data file in QB Desktop and ready migrating to QB Online, make sure to click the Buy button to get the discounted price for up to 6 months. If you purchase from the trial account, you have to pay the regular price.