This depends on which exam you have chosen to take. Go to the Certifications page and click on the preview of the exam you are taking. You can then see the pass mark by scrolling down to the 'Details' tab. The number of questions you need to answer correctly is expressed as a percentage.
Detailed information can be found in the Preparation Guide. Next to the 'Details' tab, you will find the ‘Downloads’ tab where you can download the Preparation Guide.