This could depend on what you consider the Course ID. 

If you go to any Course and click on the Settings option at the bottom of the course menu, you will find an entry titled Course Code: near the top. This is usually a name given when the course was created.

On any page, if you look at the URL for that page, you will find ...instructure.com/courses/90891/... in the URL. the number (90891 in my example) is a unique number assigned by Canvas when a course is created.

Each of these could be the desired Course ID. If you are referring to an ID number provided by your institution, then I would suggest talking to your instructor. This is a community forum for Canvas and we would not have access to that information.