9 MAX sims, working 21 hrs each a day, is 189 sim hours a day. Say 3 hrs per crew, is 63 crews or 126 pilots per day.
126/9500 = 75 days to train everyone. That is the most optimistic figure, reality is more like 4-5 months. This assumes they have the instructor staff to handle this.

Then, there will be time to bring the parked planes back on the line.

If the FAA blessed the MAX tomorrow, it could be a year before the dust settled, so to speak.