Should I report cheating to my professor? If so, how?
The professor is free to decide to reuse questions from previous exams. It's a bit sloppy, but it's her business. She can't forbid students from learning the answers by heart, she would have no ways of enforcing this rule.

It would be unethical only if the previous tests were obtained by stealing them or any other dishonest way. If it's previous students making them available, it's just students investing efforts in a dubious way.

My answer is that you should suck up your furor, try to make the best learning out of the content (why not use these previous exams as an exercise?), and ace the exam your way. You will be much happier with yourself on the longer haul than those who will just have the quick thrill with the (false) impression of "gaming the system".

Also, don't take any more of her courses, and maybe mention in the teacher evaluation that you think the exam is not efficiently testing for understanding.

As a side note, people who succeed by learning answers by heart are only tricking themselves. They invest time and money in an education but don't take advantage of the learning. I think it's idiotic.