Yomax4 meant the Iseki tractor section of the forum,
here. Your Bolens was built by Iseki, and is mechanically related to other Iseki machines.
The screen will be located behind a plate in the transmission housing somewhere. Find the hydraulic pump (It will have a big metal pipe and a smaller metal pipe coming out of it, and be on the side or front of the engine) and follow the bigger tube (this is the suction line) back to where it attaches into the transmission casing.
I suspect your filter screen will be behind the tube, but it might be adjacent (perhaps on a corner) behind another plate. There may also be a spin-on engine type filter somewhere too; I don't know. The owner's manual I have for that series doesn't mention anything about a hydraulic filter except it being something to clean if the hydraulic system is working slowly. (I don't own, and, in fact, have never even see one of these tractors) Having said that, the basic principles are all exactly the same, and the filter will be in that vicinity. Just follow the large tube back from the hydraulic pump.
Be forewarned: You'll need something like a 5 gallon pail to catch all the fluid in when you drain it, whether from the drain plug or the suction line. Good luck! Let us know how you do.