If you are looking for a particular string within a GPO, but you don’t know the gpo? Here is a good way to search group-policy for that string, and get the GUID for you.
That will grab you the GPO GUID. You can then pipe that into a “get-gpo” to find which gpo contains your string.
Further on from this, you can then do a ‘find-and-replace’ to automagically replace the string within your GPO.