Can't uninstall unarchiver?

I am very confused at what has happened when I have downloaded the "Unarchiver," which I downloaded to open things that I could previously not open; however, it has simply cause many problems and I want to uninstall it.

The problem is, I don't know how. I checked the applications and utility but I can't find the unarchiver file to delete.

When I downloaded the unarchiver, it made my default browser on Google Chrome into Yahoo, even though it says my default browser is Google. Every time I open Google Chrome, this is in the url:

chrome-extension://icdlfehblmklkikfigmjhbmmpmkmpooj/newtab.html

I have no idea what to do with it, and this has been annoying me for some time, since I don't want to always type "google.com" to go on Google. Is there anyway to remedy this problem? I thought uninstalling unarchiver would fix it, but I don't know how to uninstall unarchiver.

I already removed the extensions on the top right hand side next to the url bar, but it didn't do anything either.

Could anyone please help me? Thank you very much.