microsoft account got hacked

I'm sorry to hear about the problem with his email account. If his email account has been hacked, he should follow the instructions provided by Microsoft at this link: https://support.microsoft.com/accounts-billing/manage/how-to-recover-a-hacked-or-compromised-microsoft-account

He can also use this form https://aka.ms/recovermyaccount, which will be sent to a team specializing in this type of problem. (Although it mentions Xbox, the form is also for Microsoft account recovery.)

Use this guide to help him fill it out: https://support.microsoft.com/account-billing/guidance-notes-for-the-microsoft-account-recovery-form-4dd8fef1-33d2-4fbe-9352-66127ab9b50e

He should receive a response by email. It may take up to 72 hours.
If he does not receive a response after this period, he should check his spam folder.