Need help to save my son’s world.

Sorry if this isn’t allowed here. Delete and publicly shame me if necessary.

My son is 6 and has been playing Minecraft on my iPhone for over a year and loves it. We would like to get him his own tablet so he can play it without my phone. My question is: When we get him his own device how will I log him into his game or world? I never played video games and don’t even know where to start. I just don’t want him to lose all of his work. Help