I hope the following is what you want. The Google Groups Help says:
How do I unsubscribe from a group?
You can unsubscribe from a group through our web interface or via
email. To unsubscribe from a group through our web interface, just
click the "Edit my membership" link on the right-hand side of the
group's homepage. Then click the "Unsubscribe" button on the page that
appears.
To unsubscribe from a group via email, send an email to GroupName
+
unsub...@googlegroups.com. For example, if you wanted to leave
google-friends, you'd send an email to google-friends
+
unsub...@googlegroups.com
Please note: If you unsubscribe from a group that only allows members
to see group content, you may not be able to read that group's pages
anymore. If you want to continue your membership in a group, but don't
want to receive group email, select the "No Email" option on the left
side of the Edit My Membership page and click "Save these settings."