Open-ended question. What lift do you have? Which Jeep will the 35s go on?
The 35" measurement is at maximum sidewall width. So, if you Jeep will cleanly handle 30" tires without rubbing and you want to go to 35s, increase the width by half the difference of the tire width: 35-30=5, 5/2=2.5" posative offset.
If you are going to add them to the TJ, you will ned at least a 3" (4"recommended) lift with 1'to-2" body lift to make the grade. A TJ with 33s will work with a 3"-4" suspension lift. You may want to add a washer under the steering stop nuts located at the steering knuckle to prevent rubbing in tight turns.
As far as back spacing, Chrysler recommends a >maximum< of 1" (~24mm) back spacing to avoid unsafe steering geometry. The actual measurement depends on your rim width. For instance, an 8" rim will measure 4-1/2" at centerline (8"wheels actually measure 9" rim-to-rim). This equals zero offset in metric terms. A posative 1" offset from centerline on an 8" wheel will measure 5-1/2" from the >inside< rim, and 24.5mm out from centerline. Standard inch measurement is figured from the inside rim, and metric is measured from the true centerline. Get the idea?
Right Wrongs Nobody