Good am mga tsikot masters,

My friend left me the above mentioned car, almost 20yrs old, matanda na. I had it changed the engine and transmission oils in one of the gasoline service station. I bought a 4L transmission oil pero sabi ng mechanic 3L lang daw ang dapat ilagay. Maybe hes right but i want to check it myself if the oil he put is enough. The problem is that we (me and the mechanic) cannot find any transmission dipstick and the mechanic said wala daw siyang nakita. So now, i have no idea how to check the fluid if ever its on the right level. Anyone of the masters here know how to check the fluid level of the above mentioned car? Maraming salamat po mga masters