It you are trying to put a 3pt hitch on a garden tractor.. are you looking at cat 0?
If so... find an area you can build / attach a sub frame ro the rear of the tractor.. them with angle iron/flats.. etc.. frame out a unit that has lower arm pins.. make some lower arms out of flat stock.. attach these to an upper arm frame again that can pivot on top of the lower frame... use flats or rounds using a clevis hookup as lift links to the lower lift arm. Pipe and rounds or rebar will make easy to build pivots....You will need a power source to mount and pivot against the lower frame and press against the upper lift frame.. I've seen some people use a simple bottle jack... handle forward... pump the handle and the jack extends.. which lifts the upper arms.. which lift the lower arms.
Others have used 'ready' power units.. small 12v powered hyd pumps and small SA cylinders.. though this is a pricey way to do it. I've also seen aux pumps ( power steering pumps ) added to the belting and then the addition of some valving and a tank for 'real' hyds.. etc.
I've seen many a small farmall cub or allis chalmers B setup with the bottle jack lift.
i have even sen an old BF avery with a 12v cable winch setup with pullies to lift a light 3pt hitch.
good luck
Soundguy