For metric unit conversions, figure out if you are going to go from a smaller measurement to a larger one, and vice versa. for small to large, divide by 10, 100, 1000 depending on how much different they are. ex 987 cm = 98.7 dm.
for large to small, multiply by 10,100, or 1000 depending. ex 987 km = 9870 hm.