Question 235362
The basic rule for converting units of measure is to use units. Units will guide you through the problem.
Now, if you want to go from grams to kilograms
you need to know that 1kg=1000grams

so if you have 1.5 grams and you want to go from grams to kilograms you'd 
use this:

1.5g* 1kg/1000g= .0015kg

you would divide the number of grams by 1000grams because 1kg equals 1000 grams.

for length, if you want to go from kilometers to feet
you would need to know that 1 mile = 1.60934400000644 kilometers = 5280 feet

if you have 3km and you have to find how many feet are in there, you would use:

3km*(1mile/1.61km)*(5280 feet/1mile) 
*kilometers and miles would drop out and you would be left with feet
now
3km* 1mi/1.61km = 1.86mi*(5280ft/1mile)= 9820.8 feet