Any grade that gets the diploma is a good one! It’s a challenging course that requires a lot of commitment, so be proud of whatever you’re aiming for.
For context, however, this is the graph for the distribution of points awarded in IB. The mean score in 2019 May was about 30 points. Over 30, and you’ll be above average!
Universities differ widely in their grade requirements, though – check the university admissions section for more information.