2,000,000 mg = how many kg?
\(1kg=1,000g\\1g=1,000mg\\\\therefore\\1kg=1,000\times1,000mg=1,000,000mg\to1mg=\frac{1}{1,000,000}kg\\\\2,000,000mg=\frac{2,000,000}{1,000,000}kg=\boxed{2kg}\)