Hi @jennylee ,
Considering that you only need to migrate 25 users,, I think exporting the mailbox to a .pst file is the quickest way.
In addition, if you want to learn about other migration methods, Microsoft recommends that you use a third-party migration tool for migration.
For more information you could refer to: How to migrate mailboxes from one Microsoft 365 or Office 365 organization to another
----------
If the response is helpful, please click "Accept Answer" and upvote it.
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.