does your cherokee have a/c ?
ok i had to ask as there is some customers on here from other countries and it makes a difference.
the serptine belt is removed by loosening the power steering pump bolts and then pushing the pump in to remove the tension off the belt. then remove the belt.
here is a routing diagram.
ok i looked at it wrong below is a picture the pulley in the picture is where the tension is released, loosen the bolt that goes through the center of the pulley then on the backside of it will be a bolt that as you turn releases the tension.
the pulley will physically move in or out in the direction of which will remove or add tension to the belt. simply by you turning the bolt that is on the backside of the pulley.
are you sure that you can perform this job safely?
no you dont need to touch the power steering pump.
the information i have given you is direct from the factory servive manual.
the nut on the front of the pulley needs loosened to allow the pulley to move in a slot in the mounting bracket. the all thread piece you mentioned that has a piece on it on the backside of the bracket will have the long bolt going through it that long bolt is what is used to adjust the tension on the belt. turn the bolt counterclockwise to loosen the belt clockwise to tighten the belt.