I'm not sure exactly what you are saying. Did you find the hand histories but they wouldn't import? Or did you not find the hand history files?
If you didn't have your poker site configured to save hand histories then there won't be any yet. You should be able to request your previous hands from your site's support and then you can
Manual Import them.
Any files that are in the hand history folders already should be found and imported by the Setup Wizard which runs when you first launch PT3 (or via File > Setup Wizard).
Hand histories need to be in English - if the hand histories are in another language then they will not import. You need to have your poker site installed in English.
There are site configuration guides in the
Documentation if you need help configuring your site to save hands, or finding where the files are saved.