This article talks about Windows Defender (the free anti-virus with Windows 10) coming out on top in some anti-virus tests. Basically – there’s no reason to pay money for an anti-virus, or even use most of the free add-ons out there.
https://www.techradar.com/news/the-best-windows-10-antivirus-might-surprise-you
I do recommend that you also download Malwarebytes from https://www.malwarebytes.com/mwb-download. Use the free version if you’re ok with manually scanning once a week or so. Otherwise, get the paid version, which will do a few more things for you, and watch while you work.