you use dimensional analysis 
and conversion factors.
1 gram= 0.001 kg 
1 kg= 1000 g

(1) Starting unit  |  (3) Ending unit
-------------------------------------------
|  (2) Cancelling unit

3.2  g  |       1 kg             <-- you now just multiply an divide!
-----------------------   
|    1000g 

Multiply: (3.2g)(1kg)= 3.2 (kg)(g)
then you divide by the 1000 g at the bottom soo...

3.2(kg)(g)/1000 (g) = 0.0032 kg

you use dimensional analysis 
and conversion factors.
1 gram= 0.001 kg 
1 kg= 1000 g
(1) Starting unit  |  (3) Ending unit
-------------------------------------------
|  (2) Cancelling unit
3.2  g  |       1 kg             <-- you now just multiply an divide!
-----------------------   
|    1000g 
Multiply: (3.2g)(1kg)= 3.2 (kg)(g)
then you divide by the 1000 g at the bottom soo...
3.2(kg)(g)/1000 (g) = 0.0032 kg

you use dimensional analysis 
and conversion factors.
1 gram= 0.001 kg 
1 kg= 1000 g

(1) Starting unit  |  (3) Ending unit
-------------------------------------------
|  (2) Cancelling unit

3.2  g  |       1 kg             <-- you now just multiply an divide!
-----------------------   
|    1000g 

Multiply: (3.2g)(1kg)= 3.2 (kg)(g)
then you divide by the 1000 g at the bottom soo...

3.2(kg)(g)/1000 (g) = 0.0032 kg