Uninstall Yahoo Powered Search

I have read other answers but I am not getting what I need.

Somehow, I ended up installing this Yahoo Powered Search. It was making my search engine run Yahoo rather than Google. I fixed that problem, and only Google runs as my search engine. Yay for me!

Every so many days, this window pops up that says a software update is required,

An upgraded version of Yahoo Powered Search is now available. Set Yahoo as your homepage and default search on all of your compatible browsers and receive applicable updates from time to time.

By clicking "OK" you agree to install the above and have read and agree to the Yahoo Terms of Use and Privacy Policy.

I click on Not Now, it asks me Sure you want to leave? Yahoo Powered Search is only a click away from being up to date. Skipping on this update might prevent you from enjoying the latest Yahoo Powered Search features and fixes, that will improve your Yahoo experience. I can then click on Skip or Update. I click Skip and it closes.

I want to uninstall this so I quit getting this pop-up. I have gone to Safari>Preferences>Extensions and I do not have any extensions. I have read in other responses this is a way to remove it.

I am on a MacBook Air from mid 2011, running macOS Sierra V 10.12.5. Safari is V 10.1.1. Any help removing this Yahoo Powered Search would be greatly appreciated.