You can try the compromised-account link included above, but I’d doubt that will allow you to regain access.
That’s just not your Apple Account.
Not any more.
Whether you got phished, or somebody with local access guessed your passcode or password, or whether you re-used that password across sites, or something else happened that allowed the security breach?
Probably also didn’t have two-factor authentication enabled, as that’s a last-ditch means to maintain account control after a password compromise.
But you’ve lost control of that Apple Account.
You will want to create a new Apple Account, get your payment cards associated with that Apple Account rotated by your payment card providers, will want to reset all your passwords, and migrate your devices to the new Apple Account. Get all your mail transferred to an account you control, and messages and phone numbers and screen video captured, etc. Get a backup of your devices to a local Mac or PC, too.
Let your closest associated know they might be getting scam and phishing mail pretending to be from “you”, too.
Yeah, this is most definitely not a situation anybody ever wants to be in, either.