how to edit blog sidebar

Can someone help me with this? I’ve been looking all over for the file that controls the blog sidebar. I see for the other 4 sidebars, but not for the blog. in short, I’m trying to change the style of the blog sidebar titles and how the content of my widget displays. I was able to make most of it work in styles, but I see that there is an h3 tag that I can’t find in the templates to get rid of.

Thanks.