The term "mcg" means micrograms, right? Well, there are 1 million, or 10^6, micrograms in a gram, and 1000 or 10^3 grams in a kilogram. So that means there are 1 million x 1 thousand = 1 billion = 10^9 micrograms per kilogram. To convert, multiply the mass in Kg by 10^9 micrograms per kilogram to get the mass in micrograms.