There is a Developers site for Facebook.
Facebook Developer Page
This page has a menu of tools, including the Graph API Explorer:
Graph API Explorer

There is a Search for a field option
Click Search for a field and select accounts . Then click the Submit button.
Interestingly, this will NOT give you the Facebook Group ID! The identifier for the Facebook group seems to be just in the URL when you visit this group, FOR FREE , you edited the group settings, and Set Up Group Address . In this case, the identification number in the URL will no longer be displayed. So what do you do to find an identifier for a group? Once you have designated Group Address , no return is possible; you cannot delete Group Address .
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