This is a bit of a cumbersome task. There’s an API call to export users, but you would need to do it one by one using get/audiences/v1/audience/{uuid}/users.

Just to clarify your use case—how many groups do you have on the platform? Is this something you need as a one-time task, or do you want to monitor it regularly?

I have about 1200 groups. This is part of the clean up activity we are doing. So I might need to do this again.
This call will help me get the users that use groups in there reports?