Main and Trip Odometer reading problem.

My 1981 Mercedez-Benz 240D Main Odometer stopped working as well as the Trip Odometer. The Speedometer still works though. I drove the vehicle for a couple of miles and still both the Main Odometer and Trip does not move. The Trip Odometer showed 199 and I was able to reset it to 0000 but still the Main Odometer and Trip Odometer does not work. I know that the Main Odometer comprises of six digits. I would like to know if the Main Odometer last digit to the right is part of the Main Odometer reading or it is just the 1/10th of the mile counter?

Typically when the Main Odometer and Trip Odometer reading stops working, are the wheels of the Odometer bad or somewhere along the cable is loose?

Thanks,
Slade901