There is no "code" for a TV that works for all remotes.
Each remote has a preloaded database of IR codes. The manufacturer assigns a number to the codes for each device so the user can use them.
If your remote doesn't have the codes installed you can't add them.
Get a Logitech Harmony remote that is programmed online from their huge database of codes. If they don't have the codes already the app will prompt you to teach them into the remote and their database.