I just bought a Penguin 100 for one of my tanks that had a top fin power filter in it. Does this mean my tank will be cycling again? Sorry it's prolly a dumb question but i'm a rookie

Run both of them together for a week or two. This way you won't
go through cycling, the bio bugs can set up in the new filter. If
there is enough room in the back, I'd just leave both of them there.
That way, if need a cycled filter for a small tank, you can pull one off
and transfer it to the tank in need. I've got 2 penguin 125's running
on a 10 for just that reason.