I found it! I found it!

I uploaded the "Friends Request 3.3"plg-in then added this code in the it's start.php :

            //add menu item groups in page messages
            $userguid = get_loggedin_user()->guid;
            $url = "groups/invitations/".$page_owner->username;
            $invitations = groups_get_invited_groups($userguid);
            $invitation_count = count($invitations);
            if($invitation_count>0){
                $extra = " [" . $invitation_count . "]";
            } else {
                $extra = "";
            }
            $menu_item = array(
                "name" => "groups",
                "text" => elgg_echo("groups:invitations") . $extra,
                "href" => $url,
                "contexts" => array("messages"),
                "section" => "groups"
            );
            elgg_register_menu_item('page', $menu_item);

I hope this might help someone!