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?

Yes, exactly! Given the number of groups, you should do this operation by calling the API get/audiences/v1/audience to retrieve all the group UUIDs. Then, you can use the other API get/audiences/v1/audience/{uuid}/users to get all the users from each group.

Thank you i will try that.