QBMB format is used for one of the default backup files in Intuit QuickBooks accounting software, so qbmb to qbw conversion is most likely related to recovery of these backup files and export of the company data (.qbw) once this is done.
We have not found anything specific about this on the Internet, so if you have issues with recovery of .qbmb files, it might be best to reach out to QuickBooks support for assistance.
Updated: October 12, 2023