Ah, I see - so you're not actually looking for the hand history files themselves?
Were the hands imported as you were playing? Are the files now in the Processed folder?
If so, it is likely that you have a filter enabled - check the sidebar and clear any filters listed in blue.
If the hands weren't imported check the PokerStars Configuration Guide
to make sure that you have PokerStars set up correctly to save histories.