Write 3150 as a product of prime powers…

Step 1. Divide. $3150 \div 2 = 1575$, $1575 \div 3 = 525$, $525 \div 3 = 175$, $175 \div 5 = 35$, $35 \div 5 = 7$.

Step 2. Collect. $3150 = 2 \times 3^2 \times 5^2 \times 7$.

Step 3. Read off. The power of $3$ is $2$. The different primes are $2, 3, 5, 7$: four of them.