If you just replaced the blades, whether they are new blades or just sharpened blades, and the riding tractor is not cutting the grass at all it could be because you put the blades on upside down. Make sure the blades are installed correctly.
If the blades are on correctly, then check the belt(s) to be sure they are on the pulleys correctly and that they are on tight. If the belt shows any sign of wear or breakage you should replace it.
Depending on your Honda riding tractor model, the serial number will be located on the frame on either the right side, or front right side. The model name will be on the engine hood or above the rear wheels.
NOTE: if you need a part for the small engine in your Honda lawn tractor, there will be a separate model/serial number for the engine. Honda lawn tractors are powered by Honda engines. Visit the Honda engine page to find out where the model/serial number is located: