Question

Which conversion requires multiplication?

Answer 1

With metric measurements, the prefixes in order from smallest to largest are:
milli-, centi-, deci-, unit, deca-, hecto-, kilo-.
Converting from the left to right (from smallest to largest) means you divide to get your answer.
Converting from the right to the left (from largest to smallest) means you multiply to get your answer.  Deciliter to liter goes from left to right, so that would be division.  Liter to kiloliter goes from left to right, so it is division.  Kiloliter to liter goes from right to left, so it is multiplication.  Milliliter to centiliter goes from left to right, so it is division.