Turn your Ticketmaster ticket around so that you can see the back. The "Ticketmaster" logo on the back of the ticket should be facing towards you and should be legible. If the "Ticketmaster" logo is upside-down, the ticket itself is upside-down and you need to rotate it.
Look just above the "Ticketmaster" logo on the back of the ticket. This is your Ticketmaster order number.
Look to the right of the black square on the right side of the "Ticketmaster" ticket. This is the secondary location for the order number. This number should exactly match the number located in Step 2 above.