The current method for transferring content from a UBB.classic board to a UBB.threads board can be found in the
Admin Guide. Basically, you will need to upgrade your UBB.classic board to 6.7.2 first. (This is actually a 2-step process: first upgrade to 5.47e, then to 6.7.2.) Then use the Import/Export feature to export the data (members, categories, forums, and topics/posts). Copy those data files to the /import directory of your UBB.threads installation. Then place a copy of the UBB.classic YAML file there. (
YAML page). Then run the Import Data feature in UBB.threads. That will do it.
If you cannot get the UBB.classic 5.47e files, put in a support ticket and we can provide them.