Hyr_dolic ?
I doubt that there is one, I wouldn't want that stuff in my tractor.
IF there is one for hydraulic fluid that is likely to be somewhere around/on the rear axle.
From the back look around the top of the axle, maybe high and almost close to the seat.
Tractors are "like that", this is general guidance only.
There is also likely to be a "sight glass" for checking the fluid level, look for a glass/plastic clear "bubble" about the size of a thumbnail with one or two horizontal lines on it.
If two they represent high and low, if one it represents a recommended level.
Don't expect to find a dip stick, not saying they don't exist on tractor axles, but the sight glass is more common.
Again, general guidance; if using the tractor on steep slopes an extra gallon of fluid is often recommended.