Using front end function in admin

get_count_group() is defined in mf_front_end.php. However, mf_front_end.php is loaded only if is_admin() is not true (see main.php line 278) so get_count_group() will not normally be available in the backend. But, you can try and include this file in your backend code or alternatively copy the function get_count_group() from mf_front_end.php to your backend code.