I did this on my W201 190D. It uses the same parts as the W124, so I would expect the procedure to be similar. I posted the procedure and parts list at
Rear axle carrier (subframe) mounts / ball joints ('84 190D)
There are a total of 4 bushings on the rear axle, two on each side. One is in front of the axle and one is behind. They're pictured in the attached file; the front one is labeled 1A and the rear one is 1B.
The terms subframe mount and subframe bushing seem to be interchangeable, from what I could tell when ordering mine. The MB dealer actually called them rear carrier mounts (in case you come across that term too).
The kit I bought did the front set of bushings, it included two each of the parts labeled 1A, 1E and 1F in the diagram. I didn't do the rear, but I believe Mercedes sells a similar kit for the rear pair of bushings.
Anyway, you'll need two of each part in the attached diagram.
