To convert kilograms to grams multiply by 1000. I've generated some hopefully helpful examples randomly below, as with most random sentences please excuse the repetitive and occasionally comic outcomes.

How many grams of onions are there in 400 kilograms? Just multiply by 1000 to get the answer of 400000 grams.

To convert 0 kilograms into grams multiply by 1000 giving 0 grams.

You've got 540 kilograms of rye but someone only wants to buy that in units of grams, to change the units multiply by 1000. Now you have 540000 grams.

You have 310 kilograms of barley but you need to know how many grams that is. To get the answer multiply by 1000 which gives you 310000 grams.