safe anti virus program

Your brain. That is all the anti-virus solution you need.

We have been recommending for years that Macs don't need anti-virus software because it cannot alter the behavior to download/install ad/malware; that there are no viruses on the Mac to detect, and that anti-virus products have shown consistent interference with the operating system's built-in security.

What you do need, depending on your download habits, is the free Malwarebytes for Mac, which is purposely built to detect adware, other forms of malware that may be hitching a ride on downloaded software. It is not an anti-virus product.