How can I sign out of my old AppleID which no longer exists and sign into my new one?

Watchib15 wrote:

I purchased all on every device.

Well, since you no longer have access to that Apple ID, you will no longer be able to access anything purchased with what is now your wife's Apple ID. So once you do sign out of what seems to have become her Apple ID, you should erase your devices and start afresh. Here is how:

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

On an iPhone, for example, you could sign out of the Apple ID at Settings > [The Apple ID ... at the top of Settings] > [Scroll down to the bottom] Sign Out

Take the device, the original purchase receipt, and a photo ID to the nearest Apple Store.

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or contact Apple ID Support. They will need to see the receipt also.

Apple ID Support

Apple ID Support (2)

Apple Support by e-mail or chat Select your device, Battery, Power and Charging, then Power adapter not working to get a chat option. If you need to talk to them, ask them if they will do a Skype or FaceTime with you.

Apple Support using Twitter

"... my old Apple ID which no longer exists ..."

This is incorrect. Apple IDs are not deleted.

We need many more details of your particular scenario. A few examples:

• "Sign out ..."
  • On what device?
  • Running what version of software?
  • Why?
• "Sign into my new one?"
  • On what device?
  • On the same device as above?
  • Running what version of software?
  • Are you aware that the new Apple ID does not own anything the old Apple ID may have purchased in an iTunes or App Store?

"Everything"? Well, you'll lose at least those things associated with the old Apple ID and those things that have not been backed up somewhere (not counting iTunes backups using the now inaccessible old Apple ID). That should be pretty much everything.

Oh, she changed the Apple ID and you do not know the new one. I see.

So can you go to Settings > General > Reset > Erase All Content and Settings? What happens then?