I would be surprized if this thing stude here for that many years with out a foundation, I would like to see you dig around a little and see what's under there.
You will likey have some bad floor joists under the floor too, if it's built close to the ground.
The fix for one side goes something like this.
Remove enough floor sheeting to dig down and install a concrete footing about 18" square and eight inches deep on solid undisturbed soil, how ever deep that is.
Do this at each end of the wall and in the middle of the wall.
If the corners of the building are level with each other, build cribbing on the corner footing to about 2ft above the floor.
You build 2 beams out of something like 4 2x12 long enough to reach from the corner to the center where the jack will be.
In the center you place the jack with about a 2ft peice of 6x6 steel H beam with a cradle welded to it to fit the top of the jack to keep it centered while jacking.
On top of that fits the two beams. You set the jack height so the beam is reasonable the same height from the floor above and build a temp wall from the beam to the floor above.
With angle braces on the wall from high to low so it won't rack and braces from the new wall to old wall and from new wall on an angle to the floor above.
In other words you brace the crap out of it so everything stays together when it is being lifted.
If you find rotton floor joist or you are afraid they won't go up with the rest of the building you tie the two floors together with more braces.
The one thing about hydrolic jacks is, if it's not big enough it won't lift it.
You also set up two spots where you can shim as you go so if you have to reposition or you have a failure, you have captured all gains.