Question instances report
From MoodleDocs
An administrator can generate a question instances report in Administration > Site administration > Reports > Question instances. The Manager can also generate this report.
This report lists all the places a specific question type is used. It provides a list by course that shows the total, visible and hidden number of that question type. Clicking on a context link such as course title will take you to the relevant question in the question bank.
One practical use of this report is to find questions that may have inadvertently been created in a course which should have been created at the System default or a particular category context.