I will provide a little bit of assistance to get you started, but according to the rules of this forum, you must show your work to receive help. In general, activity is calculated as a number in µmoles per minute. Specific activity is calculated as a number in µmoles per minute per milligram of protein. Notice that what is needed is an amount, not a concentration, in the numerator. Likewise the denominator is a mass, not a concentration. The activity of an enzyme is an extensive property, and the specific activity is an intensive property.