@ SPeedFANat1c
PokerTracker4 should not import any poker hand more than once if you're doing the imports to the same database. Hands from a particular poker site are unique in that each hand has a number which no other does and PokerTracker4 uses this to ensure it only gets added once.
So as long as you're not importing into separate databases, a hand PokerTracker4 recognizes as already being in the database will be called a duplicate and get skipped over.
I'm not sure I'm completely clear on your situation but if you're converting HM1/2 databases into PokerTracker4, what happens is that PokerTracker4 first exports all hands from the HM1/2 database then imports them into PokerTracker4. This means that as PokerTracker4 is going through the new imports it will spot and skip any that were imported during a previous conversion. But keep in mind, this can only be done when PokerTracker4 is importing into the same database, which may not necessarily be the case when doing a database conversion.
One caveat about duplicates, while PokerTracker4 won't import the same hand into the same database more than once, it still does take processing power/time to determine what shouldn't be imported. So while 'skipping' sounds like an easy/quick thing, it's not really so it's always best to avoid duplicates wherever possible. Up to a few dozen/few hundred or so isn't an issue but when it goes into the thousands that might cause PokerTracker4 to become temporarily unresponsive or create other trouble.
If you run into a problem with your conversions it's probably best to open a support ticket: https://support.pokertracker.com/support/ticket/2
Include in that a link to your PokerStrategy.com forum post or a couple details about what you're doing - we'll then be able to help plan how to complete the task with the least amount of trouble.