The volume of a cylinder can be calculated using the formula:
V = πr^2h
where V is the volume, r is the radius, and h is the height.
Substituting the given values, we get:
V = π(3 cm)^2(4.2 cm)
V ≈ 113.1 cubic centimeters
Therefore, 113.1 milliliters of liquid are needed to fill the cylindrical can. Note that 1 cubic centimeter is equal to 1 milliliter.