To view what courses use a specific certificate, log in as administrator and from your Administration dashboard, visit the Certificates page.
Over there you shall see a tabular list of all your certificate templates. To view what courses are using one of these templates click on the one that interests you.
If the certificate template is used by any course a second tab will be available called Used by courses (1), click on this tab and you shall be presented with a tabular list of all courses that award this certificate.
Note: If you haven't assigned the specific template to any course, you won't be able to see the tab "Used by courses" at all.