How many kilograms are in 10 milileters?

None - they are different types of measurements. a Kilogram, or 1000 grams, is a measurement of weight, like pounds or tons. A Milliliter, or 1000/th of a liter, is a measurement of volume, like ounces or gallons.

You wouldn't ask, "How many pounds are in a gallon", so the questions "How many Kilograms are in 10 milliliters" makes no sense either.

HOWEVER, you could ask "How many Kilograms does 10 milliliters of water weigh", for example. The answer would be "not many", because 10 milliliters is about a teaspoon or so...