1999 prairie 300 carburetor line
 

there's a rubber tube about 8-10 inches with a few inches of plastic tube at the end of the rubber - this tube is attached to the very bottom of the carb. After working on the carburetor, I don't know where this line goes. Would greatly appreciate any answer on this. thanks.

From your description it sounds like the carb drain line. It fits onto the btm of carb then drops down toward the ground, sort of in between things so any overflow from the carb drips down on the ground. Not EPA friendly but that's the way things were done back then. Should only have fuel dripping out if you have a stuck float/needle valve. I had a 2000 praire 300 for 16 yrs it was a great machine. Plowed a 300 ft drive every winter and never an issue.