Hi, I'm John!
First, I want to set expectations. In some cases, accounts cannot be recovered, especially if the hacker already changed the email/alias and enabled their own two-step verification. That can lock out the original owner completely.
To confirm:
Try searching for the account using these steps from Microsoft: https://support.microsoft.com/account-billing/forgotten-your-microsoft-account-username-b2049472-3b8f-27d3-61c6-67a668453f4c Click on "Search" and follow the instructions provided.
If you receive any error messages, such as “account doesn’t exist” or anything else, please let me know.
Click "Add comment" to let me know.
Regards,
John J.D.