Merging several old wbb (burning board) and vbulletin forums to one vB 3.7.2

[DerBademeister]

I hope I posted my request in the right sub-forum.

I used several different forums for my clan over the last couple of years, and I want to merge all those forums to one vbulletin 3.7.2

The main forum we use now is a woltlab burning board 2.3.6, which according to Impex, could be imported to vbulletin.

However I have some old forums that I would like to merge as well:
- one vbulletin 2.2.6
- one vbulletin 2.2.9
- one woltlab burning board 1.1.1

I did not find converters for those old forums. There's a user-made converter that can import the wbb 1.1.1 in an empty vbulletin 2.2.x, but even if I did that, I then would be stuck with three old vbulletin 2.2.x and one wbb 2.3.6.

Does anyone have an idea how I can merge all these forums?