I d seen it on a couple google searches & on Amazon Drive.Welcome to iPhone Forums!
Do you see this in an app? If so, which one(s)?
In Amazon Drive, there's only Settings. No menu, no Autosave.
Are you sure the instructions you read were meant for iDevices?
What exactly are you trying to do? Perhaps we can help when you tell us about it.
Download the Amazon Photo app from the App Store. Sign in. In that app, you'll find the Menu bars (three lines). When you tap them, you'll find Settings. When you tap Settings, you'll also find Auto-Save.
The images from the Amazon Photos app will appear in Amazon Drive as well. It's not possible to load them to Amazon Drive directly, though.
Hope that helps.
You're welcome.