Need to check your owners manual, do not know what year your tractor was made, but the trans/hyd oil requirements changed as the years progressed.
This is a critical issue, do not put the wrong oil in this sump.
The wrong oil could ruin the hydraulic pump or trans bearings.
Let forum members know what year your tractor was made and they can tell you the correct oil to use.
Also check with MASSEY FERGUSON AGCO DEALER
Takes about 8 gals I think,
Note: have heard of some that put regular motor oil like 10w40 in this sump and say it works fine. Guess that's fine for them but would not want to place 10w40 in the trans/hyd sump on my little TO-35. It has run fine for 50+ years using the correct oil, 90 weight mineral oil, plan on continuing to use that oil.
Good luck,