Do NOT USE ATF IN YOUR POWER STEERING. The owners manuals called for this on into the eighties, but ATF has evolved drastically since then. The owners manuals were written before the formulation changes of ATF. Modern ATF is harmful to the seals in your power steering system.
Simply go into any auto parts store and get Power Steering Fluid. It is more expensive than ATF, but will work perfectly in your MB power steering system.