Your serial number is located in one of these locations:
1) On the last page of your original owners manual.
2) On a sticker on the bottom of the drip tray.
3) Behind the control panel on the left side. Remove the left and right screws, pull the knobs off, and disconnect and pull the lights off. A sticker containing the serial number will be on the left side.
4) New units will have the serial number "stamped" onto them behind the control panel on the the right side of the grill.
5) Portable cart grills may have the serial number on a sticker inside of the left door or on the backside of the cart.
Measure your cooking surface from wall to wall.