Hi @leeSophia welcome to the Nanostudio forum! This is a question, which might be better suited for a Garageband forum. I must confess, we generally have very little to do with Apple's own musicmaking app.
However, if you want a music creating app for iOS or iPadOS that has very easy access to audio effects and works with any current iPhone or iPad, Nanostudio 2 is on sale right now, 50% off! https://apps.apple.com/us/app/nanostudio-2/id1112601015