There are really two simple conversions to remember. Make sure these are among the first things you write down onto the formula sheet.
1 cm3 = 1 mL
1 m3 = 1 kL
That's it. You can rewrite your number and then just change the unit.
Of course, we're often asked to give the capacity in litres. It's a helluva lot easier to change kL to litres than m3 to litres!
It works the other way too. For example, volume = 50000 L = 50 kL = 50 m3.