I agree with the sentiments expressed here, free AV software is every bit as good as Nortons/Symantec.
There's another freebie not mentioned named Sophos as well, which is good. I'm using Win 10 and I use the built in Windows Defender utility.
However, the answer to your question is use the 2018 version of Nortons if you really must part with some cash.
And contrary to popular belief software doesn't have to be paid for or expensive to be good