https://wccftech.com/steam-owners-must-buy-hitman-2-again-to-transfer-game-saves-to-egs/

If you're looking to play Hitman 2 as part of your Hitman 3 experience, you may have to end up purchasing another copy of the game.

In its Hitman 3 Pre-Launch Guide, IO Interactive lined out its Hitman 3 Access Pass on PC. This is what ultimately will assist players in getting all three games in one place so they can play them fro the Hitman 3 hub.