The entire dipstick does NOT go in, it is a sort of universal MB thing.
You push it in until it stops, supposedly it has hit the pan.
Take the engine cover off and see approx how much distance between the top of the tube and the pan, that is how much should go in.
If that pretty well matches up with what you are seeing, then you have NO fluid.

Check the level with the car fully warmed up and idling in Park.

Here's a video :