George - Google is your friend - 1)you can search and find more about your YT 16 belts, 2) take your belt to the local big box store and start looking for one close to the same size, 3) go to your local New Holland tractor/mower store and they should have your part.
It's likely to be 1/2" x around 100" long - maybe more maybe less, but if you are matching one up off the shelf get one 1" smaller than you have now as they stretch as they age.
Good luck