Hi, @X-Box-11-2021
Thanks for posting your question in the Microsoft Q&A forum.
According to your description, you want to check which devices you're signed in to your Microsoft 365 email account on. You can try signing in to your Microsoft account with the account you want to query to see when and where you were last signed in to that account.
Refer to: Check the recent sign-in activity for your Microsoft account - Microsoft Support
If you have any questions, please feel free to contact me. If the answer is helpful, please click "Accept Answer" because it can help other members of the Microsoft Q&A community who have encountered similar problems and are looking for solutions. Thank you.
Best,
Jeanne