Each iphone/iPad app requires a series of screen shots… but all Apple Connect tells you is the screen size in diaginol inches… So after some trial and error I determined what iPhone model to use in the simulator for each one
- iPhone 6.7" - 15 plus
- iPhone 6.5" - 12pro Max
- iPhone 5.5" - 8 plus
for iPad it asks for 13" and 12.9"… why I don’t know as both are the exact same resolution
- 2732 x 2048
hope this saves others a few minutes of research