How can Copilot be used during the Microsoft certification exams?

No you cannot use any AI in an exam https://learn.microsoft.com/en-us/credentials/support/exam-and-assessment-lab-security-policies#ethical-conduct

For information on the question types https://learn.microsoft.com/en-us/credentials/support/exam-duration-exam-experience#question-types-on-exams

Check the scope of the exam i.e., the topics covered in the questions by reviewing the study guide for the exam e.g., https://learn.microsoft.com/en-us/credentials/certifications/resources/study-guides/mb-330