You will need the model number off of the mower. It is usually under the seat. Go to www.managemyhome.com and enter your model number in the appropriate box on the right side of page. You can view and download manuals that are available.
I have a Craftsman DYS 4500 and there is a nut under the left rear fender next to the tire that adjusts level. I'm still having trouble getting the deck tuned again despite my best effort with a bubble level, but that nut is definitely adjusted it.
1 ton = 2240 lb ~= 1016 kg ⇒ 4500 kg ~= 4500 ÷ 1016 ton ~= 4.42 tons I suspect you meant "How many tonnes are in 4500 kg?" (1 tonne is a metric ton.) 1 tonne = 1000 kg ⇒ 4500 kg = 4500 ÷ 1000 tonne = 4.5 tonne. 1 kilogram = 2.20462262 pounds