Was it difficult to move your saves from games on your PS5 to PS5 Pro?
Nah. I had mine in my SSD, installed it on my Pro, and everything was there when I completed setup.
Worst case scenario, assuming you've got PS Plus, your saves are automatically backed up online. You can pull your saves down whenever.
Alternately, if you don't want to do either of those, in the initial setup, it gives you an option to transfer all your data from the internal drive of another PlayStation on the same network. Just have both on, plugged in, and whatnot, and let the Pro do its thing. It takes what feels like forever, but it's an option.