I'm not familiar with your tractor in particular but after checking some pictures, it doesn't seem to be much different than the newer series. The hydraulic suction filter on the newer is located just under the 3 pt control lever. It's hidden behind the rear right tire. Since your tractor has the fuel tank also on the right side, I'm thinking the filter might be hidden behind the tank.
Another way to find it, is to follow the suction line from the Pumps all the way to the transmission.