For most of the search queries, the VBB format stands for unknown or backup files. On various websites, this format is used by an application that stores backups of various locations and since there is no actual software, I can conclude that conversion from VBB to MP3/MP4 is actually not possible.
I've also extended the search to other websites as well, but I didn't find anything that confronts my theory which means that I am right and conversion is not available.
The format might be proprietary as well, which means that unless the developers create a dedicated converter, then this process is not possible at all.