Any movies you actually “purchased”, or “rented" (Apple TV+ is a subscription service and does not sell or rent anything) should be available assuming you are logged into the Apple TV app with the same account credentials the movies were purchased with. Normally you open the Apple TV app and navigate to the “Library” section near the bottom of the menu. Your purchased movies appear there.
Now if the movies you purchased were bought on a different movie site than Apple TV, ie. Amazon Prime, of course those movies will not appear in the Apple TV app. There are two main movie purchase aggregation apps out there that you link your various sources to the app and all the movies will be there. One is called Movies Everywhere, the other is Vudu.