that's a pretty standard lawn tractor but a few yrs old... for what reason would you want to be raising the deck higher now?

I would like to cut the grass a little higher because when i cut it now it is burning the lawn

I see. Trying to further raise the cutting height on that tractor could involve replacing all 4 rims/tires with larger sizes - a considerable investment.
You might look at 1) making sure your deck blades are properly sharpened; 2) adjusting your grass cutting schedule to where you don't have to take off any more than about 1/3 of the grass's full height to have it properly trimmed and 3) cut back on any fertilizer applications currently being made.
Also, make sure your deck is leveled per your operators manual - it will help.
BTW - are the burned spots coming from your tractor's engine exhaust made when the engine is running but the tractor is not moving ?

If you think it is not raising the deck high enough, have you checked the air in the tires?
Underinflation of tires is often the cause of uneven cutting heights and if all are underinflated, the cutting height will be low all around.
Making sure all the tires are inflated to the correct pressure is the first step one should do when checking deck height.