I need a diagram for replacing the belt in the mowing deck of a Toro 17-44HLX riding mower

Check under the foot rest panel, frequently there is a decal with a diagram. You have one more pulley on the deck than you have blades, the extra is the spring loaded tensioner. Put the blet around the 3 blade pulleys and then toward the tensioner. The tensioner needs to be retracted, likely be another sety of hands. Put the belt around the tensioner so when you release it the belt becomes taught.