resolutions

Does anyone want to share an app I can use as a template to get started on building a simple iOS app that adapts to all current iPhones and iPads? This will be my first iOS app. What I want to make is an iOS version of this Android app I made a couple years ago...

PHONES Galaxy II: 480x800 = 240x400 Pixel 2XL: 1440x2880 = 320x640 or 720x1440? and for landscape, I assume I merely flip x and y? TABLETS Amazon Kindle Fire: 1024x768 = 512x384 Galaxy Tab 10: 1280x800 = 640x400 Galaxy Tab S4: 2560x1600 = 1280x800