For those looking for mock exams, here's the ones that I found very helpful.
Make sure the test you are using references PMBOK 6. You should target 75-80%. Build up your testing stamina. You need to be able to do 60 questions without a break. Use a timer to track your completion rate.
BEWARE: There's a lot of PMBOK 7 here (like tailoring) and that is not on the 2021 version of the exam.