Unfortunately, you can't simply map number of questions correct to a raw score. The GMAT is adaptive and weighs difficult questions that you get correct/wrong differently from easier questions you get correct/wrong.

The only way to really gauge your performance is from practice tests, particularly from GMATPrep.

All the best,

You will get about half of the question right and about half of the questions wrong, even if you score a 700. That's the way the test works. It is NOT scored the way we are used to tests being scored, so if you go into the test with the mentality that you have to get a certain number right, that will cause you to make decisions that will not let you maximize your score.

All you can do is accept that you're going to get about half of the questions wrong.