Have you isolated where the leak is coming from? A loose or blown hose? Valve block? Can't really help to much without knowing where the leak is originating from. If it's hard to find, clean the daylights out of it with a pressure washer and a degreaser. Once dry you can use flour, baby powder, or something similar on the parts. Once the tractor is running, the flour will show the seep pretty quickly. If you can, post some pics.
The tractor supplies the oil to the backhoe. Use a JD approved J20C or D oil, whatever you are using for the tractor. :good2: