Whenever you have a number without a decimal like this one, the furthest number on the right is the ones place (in this case it would be 1). One place left of that is the tens place (the number 2). Going left again from there is the hundreds place (where the 3 is).
So you can read it like "three hundred twenty one" or 300+20+1.
Hope this was helpful. Please let me know if you need any clarification.