There are two methods: using common sense and using dimensions. For common sense, answer the following questions.
(1) Since 5 microliters contain 1,000,000 copies and 1 microliter is 5 times smaller than 5 microliters, how many copies does 1 microliter contains?
(2) Since 1 milliliter is 1000 times bigger than 1 microliter, how many copies does 1 milliliter contain?
For dimensions, we know that there are 1000 μl per ml. How to combine and to get copies as the answer? It's ; then μl cancels out to leave .