Before you search for your groups, make sure that you’re in the organization view instead of the public view.
Go to Groups and click My groups.
Click Switch organization view to "yourdomain.com".
This means that the groups you see and join will be within your organization, and not public.
To search for a group, at the top of any Groups page, type a word or phrase in the search box. To help you search faster, Groups suggests search terms as you type. Click one of the suggestions to open it, or click to see a list of results.