A question will nearly always be written in the following way: Express 100 as a product of its prime factors
This topic involves breaking down (decomposing) numbers into their prime factor products. For example, $100 = 2^{2}\times5^2$
Once you have all of the prime factors, you multiply them to give the final answer: $$100 = 2\times2\times5\times5$$
Because there are duplicates, we collect them together as indices: $$100 = 2^{2}\times5^2$$ A very common error is for students to write the answer as 2, 2, 5, 5. If you check the question again, it asks for the product which means multiply.