Where to find the model and serial on a Spirit Fitness treadmill?

The belts for treadmills are largely universal in design. Simply measure the old belt and order one of that specification. That is the way I handle it.
 
If I purchase a deck belt without the -02 would it not physically fit to the treadmill deck?

It will physically fit however, the friction coating of the treadmill deck was changed during the manufacturing of the treadmill which could lead to the treadmill deck wearing down faster when using the treadmill with the incorrectly specified deck belt.