In the case of insulin, an International Unit (IU) is equivalent to 0.01 ml or 0.01 cm³ . In some syringes, a "cylindrical" indication is represented by the symbol "cc". Although incorrect (right is cm³), an equivalence is maintained (0.01 cc = 0.01 cm³ = 0.01 ml = 1 IU). Remember the equivalence between IU and ml or cm³ for insulin.
So considering that 100 units = 1 mL (100 x 0.01 = 1mL), 47 units will be 0.47 mL (47 x 0.01 = 0.47mL).