Glad you worked it out - for reference if anyone else finds this thread: HEM uses a different database structure so you will need to re-import your hands to your new PT3 database. If you still have the original hand histories you can import from those, but otherwise you will need to export your hands from HEM.
After you do the
Manual Import you should run housekeeping with the Rebuild Cache option - this will be much faster than using Update Cache at the end of the import, so if the import hasn't finished yet I'd recommend disabling the housekeeping options on the Manual Import tab and using Database > Housekeeping with "Rebuild Cache" ticked as well as the defaults.