How many liters are in a mega liter?

Answer 1

The question does not make sense. A millimetre is a measure of distance while a megalitre is a measure of volume. The two measure different things and, according to basic dimensional analysis, conversion from one to the other is not valid.

Answer 2

There are 1,000,000 litres in a megalitre.
as simple as needed: 1000000 L = 1 ML

Answer 3

When you're dealing with units of measure, "mega..." means "million ...".