Break it down in pieces.
204: What 2 numbers can you multiply to get 204? (it is an even number, so we know it is divisible by 2) 204 = 2 x 102 → 2 is prime so let's factor 102
102: What 2 numbers can you multiply to get 102? (it is an even number, so we know it is divisible by 2) 102 = 2 x 51 → 2 is prime so let's factor 51
51: What 2 numbers can you multiply to get 51? 51= 3 x 17 → both 3 and 17 are prime so we are done!
Answer: 2 x 2 x 3 x 17 = 2² · 3 · 17