There only seems to be a vBulletin 4 importer for bbPress. Due to the significant number of database changes between vBulletin 4 and 5, that one will not work with vBulletin 5.
Your best bet is probably to reach out to bbPress or post on their forum since people who moved from vBulletin 5 to bbPress likely aren't present or active on this forum anymore. This might be a good start
https://bbpress.org/forums/topic/vbu...ess-migration/