I don't know the number, but I can tell you how to do it. The method I will describe is the method that is a test question on the ASE test. I have used this method a number of times on MB's with good success.

Start by getting about four quarts of regular P/S fluid from your auto supply.

Suction as much fluid as you can get from the reservoir.

Put a drain pan underneath the pump, disconnect the return line from the pump. This is the one that is held on with a hose clamp. Lower this line down into the drain pan.

Be ready with two quarts of P/S fluid and have an assistant start the engine and turn the wheel back and forth lock to lock. While the assistant is turning it back and forth pour in P/S fluid keeping the reservoir full until you are out of fluid. At that point have the assistant stop turning the steering wheel regardless of its position.

Run engine until fluid stops coming out of the return line into the pan. As soon as there is no fluid coming out that line, have your assistant stop the engine immediately.

Reconnect the return line to the pump and fill the reservoir with fresh P/S fluid. Have the assistant restart the engine and fill the reservoir as it pumps the fluid into the system. Again turn the wheel lock to lock to bleed the system.

This may sound a little involved, but it takes about fifteen minutes.

Hope this helps,