App Store Connect accepts PNG or JPEG screenshots at the exact pixel sizes below, up to 10 per set: one set per device size and language. iPhone, iPad and Apple Watch screenshots can be portrait or the same size turned sideways; Mac, Apple TV and Vision Pro screenshots are landscape only.
Screenshots appear on the product page in the order of the set. In TakeOff you can drag them into a new order or add new ones per language and device; both go to Apple with the next push.
TakeOff checks every screenshot against these sizes on your Mac and routes it to the matching set before upload.