As a caveat if you are going to ubbthreads.
The importer script only works with a functioning classic board. It does not import a classic export file into threads.
At least as far as I know from when i upgraded.
So that means if you don't have your classic board running even the old version(which I believe will import to threads). You may be starting with a completely clean slate no posts from the prior board.

Of course whatever the problem is you have now may not impact the conversion(import).

Blue Man Group
There is no such thing as stupid questions. Just stupid answers