Help, lost my manual

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I had to hitch up my backhoe attachment last winter and today I finally got it unhooked and my bush hog put back on. The backhoe had a pertty good hydraulic leake so I toped off the fluid. Since I have lost my manual, I am unsure what, if any oil goes into the Hydraulic Tandem Pump. Found a picture online without a fill plug, the one on my tractor has a fill plug. I am assuming that, that is what it is called? Thanks for any help.