I have a yard king riding mower, with a 36" deck 18 hp. Can't find serial number or what size belt it needs. Can someone please help?

Hi,
Yard King was Murray's idea of a step-up line. Supposedly a bit heavier duty and more durable; as a general rule they were. Two 36" decks existed; one with two belts(early) and one with one(late.)
As a general rule the model number(it will end in "x89") is on a tag on the rear frame or under the seat with a date code. Most did not have a serial number. If you will provide the model, type and code numbers off the engine, I may be able to get you the parts breakdown.
Anyway here are both 36" decks:
Peace,
Clarke