First of all, we need to know the conversion relationship between milligrams and micrograms. In the unit of measurement, 1 mg is equal to 1000 microgram ug, in other words, 1mg is equal to 1000ug. Now, this problem can be expressed by a mathematical model: 100mg times 1000 equals 100000ug. This formula tells us how to convert milligrams into micrograms. Through calculation, 100 mg is equal to 100000ug.