See attached link for the diagram.
The belt is part number m124895 which is a 1/2" x 115" belt.
Is the engine a single cylinder or a twin cylinder? How many spark plugs? If it is a twin cylinder the belt part number is XXXXX That is a it is still going to be a 1/2" by 115" belt if you go with an aftermarket belt. Both of the part numbers are a little longer than 115" on the original belt, but the only way you can get the exact belt is to go to the John Deere dealer.
See attached link and download the manual. It will walk you through removing the deck.