A blog is usually a series of Posts (as opposed to pages). It is hard to know how you have Wordpress set up but check your Post's section and look at the categories. If there is a Blog category check what the entries for the Name and Slug are.
A blog is basically an archive page of a particular category. Unfortunately depending on how you set up Wordpress this can also be set via a custom post type in your theme. The best solution is to change it through the Admin panel if it is available, that way any future updates will preserve the change. This isn't always the case when manually editing the php files.