There should be a fill cap somewhere, but it sounds like there is no dipstick. Look around on the transmission itself, it is usually red with a symbol of a transmission and the word "FILL" on it.
My 2002 Pontiac Grand Am SE has no dipstick as well. Most automatic transmissions don't come with a drain plug. I tell my friends about it and they don't believe me until I show them there isn't a dipstick. I want to be able to check the level and condition of my fluid, but it just isn't easy, but it is possible.
To change the transmission fluid you drop the pan, change the filter(if desired), replace pan along with a new gasket, fill with the proper amount of quarts, hoist the car up, run the engine for 5 minutes, with the engine running for five minutes shift through all the gears, put it in park, pull out the little "level check" bolt on the side of the transmission and continue filling the transmission until it dribbles out of the hole, replace the plug.
It is a complicated process that could be much simpler. In a perfect world all automatic transmissions would have a spin-on filter(no pan drops), a drain plug, and there isn't an excuse for not having a dipstick.
EDIT: The manual with my car says that it doesn't need changing, unless it is severe service which would then be 50,000 miles. I know people with the same car as I have and they don't drive hard and their transmission fluid comes out dark with a burned smell at 50,000 miles. I will never follow the transmission fluid intervals set by any auto manufacturer, especially GM ever again.