A iPad art and drawing storing question. Please help

I draw on the app procreate, I want to keep all my drawings on the app since you can always go back and edit them ok? But that takes up so much space on my already small spaced iPad (can't afford another. Got this from a old friend)
So IF I have to take em off the procreate gallery, what private storage service has a light download app and is easy on data? (I have a slow shitty service on my phone but it allows mobile WiFi hotspot)
So I can store all my drawings forever safely keeping it there forever?