Hello xuetao wang,
Thanks for your question
If they are Azure accounts, you will need to contact the global admin in that tenant help prompt a reset of your MFA methods if you do not have access to the app again if it is a work/school accountin Microsoft. For other apps you will have to contact their admins
Ideally if you have the old phone you need to backup: https://learn.microsoft.com/en-us/answers/questions/1663963/how-can-i-transfer-my-microsoft-authenticator-app
If unfortunately you can't do any of the above, the only resolve this by contacting support or asking your admins/support to reset your account https://learn.microsoft.com/en-us/xandr/curate/troubleshooting-multi-factor-authentication-mfa?source=recommendations
To contact support you can call the Global Support lines here: https://support.microsoft.com/en-us/topic/customer-service-phone-numbers-c0389ade-5640-e588-8b0e-28de8afeb3f2
You can mark it 'Accept Answer' and 'Upvote' if this helped you
Regards,
Abiola