Details about the backup / restore process are here.
https://support.microsoft.com/en-us/account-billing/back-up-and-recover-account-credentials-in-the-authenticator-app-bb939936-7a8d-4e88-bc43-49bc1a700a40
but it sounds like there wasn't a backup to begin with however if it's also been overwritten then you'll need to use each of the service provider's methods of account recovery.
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