Amazon Music on iOS

I’m considering the jump to iOS from Android. Is there a way to get music that I own (mp3 format) that isn’t available in the Amazon music catalog (I’m an Amazon Unlimited subscriber) onto an iPhone that I can play from the Amazon music app? I can do it on Android, by dropping music into the correct folder. But, I’m assuming iOS is locked down.

I know I could always put my personal music in iTunes (or whatever Apple is using these days) and get it onto my phone and play it via Apple’s app. But is there a way to play it from the Amazon app?