The short answer is that ‘no’, you probably don’t need specialist anti-virus software. Here‘s an excellent article on the subject – make sure you read past the first few paragraphs.
However, it would be a very good idea to update you version of Mac OS to either Catalina or Big Sur if you haven’t already updated.
At Sussex Smarts, we’d be very happy to help with this, although it should be a straight-forward process. The critical thing to do is to make sure that you make a Time Machine backup before you start.
Sussex Smarts 