How do I find out where a Group(s) is being used

[JamesRV]

Is there a way to get list of all SharePoint sites/OneDrives that a group has been granted permissions?

We are in the process of migrating over from Windows AD to AAD and there are 1000's groups in AD that we are trying to decide if they are needed or not.  I have a feeling that m any of these groups are legacy and may not be in used but there are few sceptics that predict that there is going to be huge user disruption as these groups "might be used to grant permissions across SP/OD"

[#2]

There is nothing built-in by default.
You would have to write a custom script to do these checks