It sounds like you might be a student taking a class at your school within Canvas. Not all instructors make the "Assignments" course navigation menu (typically found on the left-hand side of your course) visible to students. The reason for this is that instructors can build out the layout of their course via the "Modules" screen. So, it is very possible that your instructor has chosen to hide the "Assignments" course navigation menu. If that is the case, then you might find the name of the assignment somewhere within your "Modules" screen of your course (hopefully, your instructor did not hide the "Modules" course navigation menu!).
Hopefully, you'll be able to find your assignment on the "Modules" index page. If not, I recommend reaching out to your instructor directly. You can do this in Canvas by following the steps in this Guide: