The second and the most surefire way to locate the id, is to open steam inside your favorite browser and navigate to the mod you like. So for example if we want S+ in ark, you would log into steam on the web, navigate to the store page, scroll down on the right and click on VISIT THE WORKSHOP link. There is another link higher up in the page that says Steam Workshop, that link takes you to all the workshops on steam and is not what you are looking for.