Check it out with a manual for your model year.
Do a search, this item has been discussed many times. MF changed their requirements as the models changed, so it is not an easy answer without knowing the year model.
My tractor is a TO35, 1957 model, it takes 90 weight mineral oil, old school oil to protect the yellow metal in the transmission.
However many changed them over to 10w30 motor oil, should be non detergent, but do not know if you could find that oil on this side of the pond.
Take tractor out and get the transmission oil as hot as possible like plowing, etc: then let it drain all night. You want to get as much old oil and dirt out of the sump. Some wash the sump out with kerosene, I did not, was concerned, my system worked well, I was just performing general maintenance.
Takes about 8 gals to refill, I bought my oil at NAPA, they can order it for you. No filter on the older models.
Again do your research and buy the right oil!!!!!