what are those men what are they doing to millie and why? in pages 11-20

I think you are referring the technicians. They arrive at the house, pump Mildred's stomach and give her a complete transfusion with various technological instruments. Neither of the paramedics are doctors, a fact Montag finds surprising. However, the paramedics explain that they perform these same procedures many times a night, and that it is a very regular occurrence. When the medics depart, the relieved yet shaken Montag reflects on the impersonal and tragic nature of his society.