Do you want to know how the metric system works? Knowing the metric system would be very useful.
Firsy, you'll need to know what, milli, centi, deci, deka, hecto, and kilo are on a scale.
To change your meausurement to a smaller measurement, you would move the decimal to the right.
From left to right, it starts with kilo, then hecto, deka. After deka we have the base unit. Then deci, centi, and milli.
If you're changing your measurement to a bigger measurement then you would move the decimal to the left.
Kilo, hecto, deka, base unit, deci, centi, milli
To know how many times you move the decimal to the left or right, you would use the scale to help you.
Say you're measurement is kilo and you want to convert it to deci. You would count each unit (including the measurement itself) until you finally hit the deci. That would be how many times you would move the decimal to the right or left.