The Default Gateway is also the address of the router to which you need to connect to be able to see the security details. That has to be done by cable because until you're connected wireless, you can't contact the router by that method. That's an added security level because normally, one would only be able to wire to one's own router. Without knowing that gateway code, you cannot go any further so use a cable and run the ipconfig /all command again and then the gateway will be shown under your ethernet adapter connection.