So assuming that your conversion rate is in fact Vmax and not only V at
some arbitrary [S], you need the molar concentration of the enzyme. This
you can calculate from the molecular weight if the enzyme concentration
(mg/ml or the like) is given, which you didn't supply.
Oh, and when you do the calculation don't forget to convert all values
to basic units, so you get the order of magnitude right! Most errors
occur at this point.