Your answer would be the third option, 3.6 cm².
The equation for the area of a parallelogram is the same for the area of a rectangle, which is base multiplied by perpendicular height. Because all of the answers are given in cm², we should convert all lengths in mm to cm.
This means that 18mm because 1.8cm (by dividing by 10).
Now we just do 1.8 × 2 = 3.6cm²
I hope this helps!