QBB is a file extension for a backup file format used by Quickbooks desktop.
There is no way to directly import QBB file to QuickBooks Online (QBO).
You will need QuickBooks desktop version program to restore this backup company file. Here is more information on how to restore a backup company file in QB desktop version:
https://community.intuit.com/articles/1436903-restore-a-backup-company-file
You can then import from the QB program itself (a QBW file) to QuickBooks Online (QBO). If you need to download a 30-day free trial program, see the link below.
https://community.intuit.com/articles/1207255-quickbooks-desktop-trial-links
Here is a helpful article that should walk you through the conversion from QBDT to QBO process:
https://community.intuit.com/articles/1145375-import-into-quickbooks-online-from-quickbooks-desktop-for-windows-us-only