I'd do this step by step to avoid confusion.
So first, I'd convert 54 km to m (and I know that there are 1,000 m in a km).
So, 54 km to m = 54,000 m.
Now, I'm going to convert 54,000 m to cm (and I know that there are 100 cm in a m)
So, 54,000 m to cm = 5,400,000 cm.
Therefore, the final answer is 54 km = 5,400,000 cm.
