I mean, if you really want to know nipple amount you could see how many kids wookies normally have at a time.
He's gonna have pecs because he's bipedal tho. Those are arm muscles basically.
If wookies have a litter, then the females would have rows of teats, but they'd only have pecs with the top two. And they'd be basically invisible on a male.
So, we know Chewy has pecs, it's the existence of teats that is unknown