The W202 C-Class and W203 C-Class C230 models do not have a dipstick for the tranny fluid as they use the 722.6 five speed automatic. You'll have to buy the dipstick from the dealer.
Also, on the 722.6, the tranny fluid level must be set while the fluid is at 80C. Use ONLY the MB synthetic fluid, or you'll probably wreck the tranny.
I don't recall the tranny having a drain plug.
1998 C230 "Black Betty"