First, you need to convert all units to calculate what dose the doctor ordered.
1 dram = 4 mL
So, it must be given 4 mL of medication
1 cc = 1 mL
So, if the vial states that there is 1 mg in 1 cc , that means the concentration is 1 mg in 1 mL or, 1 mg/mL.
Now, we need to calculate what is the dose of medication in 4 mL:
1 mg is in 1 mL, how many mg is in 4 mL:
1 mg : 1 mL = x : 4 mL
Crossing the products:
x · 1 = 1 mg · 4
⇒ x = 4 mg
