To convert grammes to kilogrammes divide by 1000. I've generated some hopefully helpful examples randomly below, as with most random sentences please excuse the repetitive and occasionally comic outcomes.
You've got 9 grammes of platinum but someone only wants to buy that in units of kilogrammes, to change the units divide by 1000. Now you have 0.009 kilogrammes.
In 8 grammes of gold there are 0.008 kilogrammes, to achieve this take 8 and just divide by 1000.
To convert 8.2 grammes into kilogrammes divide by 1000 giving 0.0082 kilogrammes.
You have 7.3 grammes of ruby's but you need to know how many kilogrammes that is. To get the answer divide by 1000 which gives you 0.0073 kilogrammes.