Upgrade from 5.9 to 5.16 in Drupal - upgrade script won't run
If you go to CiviCRM's Administer menu » Administration Console » System Status you should see an error "Database Upgrade Needed".  There should be a link you can press that should bring you to the upgrade page.  This link should account for issues like those mentioned by @Demerit.  Please edit your question if this doesn't resolve the issue.