for some reason a lot of my searches on Firefox are not being done by Yahoo how do I get rid of them.

Perhaps an Extension you have installed or updated in the Firefox web browser recently added this as a search engine? https://support.mozilla.org/en-US/kb/change-your-default-search-settings-firefox The desktop Firefox has not come with Yahoo as one of the default search engine options since Firefox 57.0 https://support.mozilla.org/en-US/forums/contributors/712925

See support.mozilla.org/questions/1568176 for more links and previous discussions.