3 devices on same Apple ID

create your new Apple ID(s)

How to create a new Apple ID - Apple Support

Then for each device that you that will be signed into a new account, follow this.. basically sign out, reset to factory settings

What to do before you sell, give away, or trade in your iPhone, iPad, or iPod touch - Apple Support

Set each device up from scratch.. signing in with the new Apple IDs. I'm assuming you are family members? Learn how to use family sharing to share content

Set up Family Sharing - Apple Support

you should not be using the same Apple ID, each person should have their own.