If the actual figure is a rectangle that is 120 meters by 400 meters, what are the dimensions of a scale drawing in centimeters?

You need to know the scale.

Divide the dimensions by the scale to get the drawing dimension.

For example, for a scale of 1:500,
120 m /500 = 0.24 m = 24 cm
400 m /500 = 0.80 m = 80 cm

and so on.

Familiarity with units conversion is a definite asset in these problems.