can someone help me with this math problem pls? How would I show my work in this question?

(3 * 10^9)= 3 * 1,000,000,000 = 3,000,000,000
(5*10^6)= 5 * 1,000,000= 5,000,000
5,000,000* 3,000,000,000 = 1.5*10^16
1.5 is the beginning of your zeros and 10^16 is the zeros after the number