https://forum.xentax.com/viewtopic.php?t=10536
Xentax is a place where you can find a lot of information about exporting models from games.
In short, on this page, there is a script for the Noesis program, which, judging by all, can be used to open a model from your game. You also need to find out how to open the archives. Search for information about this on Google.
I don't know for sure, but I got the impression that you can't extract animations and skeletons from your game. This means that you will have to use, for example, animations and skeletons from creatures from Heroes 5, or create your own.
In short, the short answer to the question "can models from Prime World be imported into Heroes 5?" will be "it seems possible, but it will be quite difficult."