Pointing to menu_anchor from within the page

I want to design a button so that when someone clicks on the button, it scrolls down to another section of the page defined by a menu_anchor. How can I do this – what URL do I need to point to in the button shortcake? For example, if the button needs to point to the contact US section with the menu_anchor “contactus” – what URL should I input in my button?
Thank you!