Hi @ Lori Collins,
Thanks for posting your question in the Microsoft Q&A forum.
According to your description, you want to know how to export an Exchange mailbox calendar and import those events into a 365 group/team calendar. You can try the following:
- Sign in to the Exchange Admin Center and navigate to Recipients > Mailboxes.
- Select the mailbox you want to export, click More options > Export to a .pst file
- Open Outlook, select File > Open & Export > Import/Export > Import from another program or file, and then select Outlook Data File (.pst). Then browse and select the .pst file you want to import, select Next, and then select Finish.
- Go to the Calendar view and find the imported calendar events in the folder list on the left. Select these events and drag them into the group or team calendar.
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