.765grams convert it into kilograms
Although we often say "converting to kilograms" or to some other units, it is not realy converting in the sense of changing the quantity. Everything stays the same, so you should think of this rewriting the expression like you can rewrite a mathematical expression. It is far less confusing to think of it this way.
So, you can write
0.765 grams =
0.765 (1/1000) * 1000 grams =
7.65*10^(-4) kilograms