Since the current importer doesn't function for anything lower than v7.5.6 (the original importer worked for v7.2) users migrating from UBB.Threads6 or UBB.Classic may see problems with their groups; imported content using the UBB.threads importers can assign your users v7.0 Group Numbers vs v7.2 Group Numbers:

v7.0 Groups:
1 - Administrator
2 - Moderator
3 - Users
4 - Guests

v7.2+ Groups:
1 - Administrator
2 - Global Moderator
3 - Moderator
4 - Users
5 - Guests

As the users are not assigned any forums to "moderate" there isn't really any concern, we just need to place them in their proper groups. You'll need to migrate the Moderator and User group indications to a higher id. As the Global Moderator group doesn't exist from the imported UBB products, we don't have to account for it.

Here we are moving group #3 (old users) to group #4, and group #2 (old moderators) to group #3 (in this order)
SQL Query

If you are using a different database prefix (other than ubbt_) you'll need to account for it in the queries. I would execute both queries separately, but in the exact order that they are presented (if you run the second first you'll have to re-assign your moderators, and may have to remove duplicate entries in the user group for them).