Remove Users from Group with API

Hi! I am trying to string together some API calls to remove members from a group. I am very confused by the IDs and process in the API Docs. https://developer.zendesk.com/api-reference/ticketing/groups/group_memberships/#delete-membership I have the ID of the user, and I have the group ID, but when I call the API, it says resource not found. I don't think the Group ID I am using the same group ID they want, but not sure where else to get it.