How do you convert 6.59 kL to L?

You use a simple conversion factor.

Before doing any calculations, take a look at the units you are dealing with.

In your case, you need to kiloliters, kL, to liters, L.

If you look at a metric conversion chart, you'll notice that kilo denotes a multiple.

More specifically, the kilo prefix denotes a multiplication factor of 1000.

So, in order to get from one kiloliter to one liter, you need to multiply the starting unit by ##10""^3##. Simply put, one kiloliter contains 1000 liters.

##6.59 cancel("kL") * (10""^3"liters")/(1cancel("kL")) = 6.59 * 10""^3"L" = color(green)("6590 L")##

Btw: ##kL## is hardly ever used. If you refer to ##1000L## you use ##m^3## (=cubic meter). It's the same.