How many milliliters are in 28 centiliters?

Millilitres is VOLUME- a measure of content or capacity, usually expressed in units that are the cubes of linear units, or in simpler terms, what fits in a certain space.

Centimeters is a LENGTH. -That means the physical distance between the start and end of some kind of linear object.

There is no similarity between LENGTH and VOLUME. They CAN NOT be 'converted' to each other.