Recover the startpage of safari

When I open my safari, it indicates the search-alpha. but I have checked my setting and it indicates the start page of apple. I think I have the same situation in this articleRemoving "Search Marquis" / "Search Baron… - Apple Community. It mentioned that maybe have some questioned document, in my computer. I really want to recover my start-page, so I follow the steps in this article, but I'm not sure which documents I need to delete. I need some help.