I think the model grader is a 120 , its about 4 years old. Anyway why would that unit be sold with out an air drier? Anything with an air system should have a drier shouldn't it?
I believe the drier is an attachment more For cold climates in which case you might Want to add one.
If its a 120M it should be hydraulic brakes with no air compressor or air system.
Exact model please and at least the 3-letter Serial Number prefix and we can tell you what it should have. If it's an M series see the answer above.