Sophos caught some but not all of a malware download on my mac

I downloaded a 'download converter for safari' on my mac and it downloaded all this malware instead. Sophos caught some of it, but not all of it and I have been going around getting advice and doing what I can but I want to know how to make sure it's really gone gone?? It's called "Play Search Now" and was taking place of Safari search engine. I am very worried as I have had a very malware free mac and don't want that to change.

Can you indicate what I can do to ensure the issue is obliterated? 

Thanks