Least to the greatest. 2,720 ml 24.91 l 0.0268 kl

First, convert every measurement to the base unit, liters. Make sure that the correct measurement is on the bottom. In this case, we want to get rid of the mL measurement, so we put it on the bottom so the two mL's can divide and cancel out:

2,720 mL * 1 L / 1000 mL = 2.720 L

Then for kL:

0.0268 kL * 1000 L / 1 kL = 26.8 L

Now that we have all of the liters measurements, we can see which is the least and which is the greatest measurement:

2.720 L < 24.91 L < 26.8 L