Software to detect and remove Malware or Keylogger

Won't go into details, but I need to check if I have Malware or Keylogger in system.

I am so a noob, so wanted to install finder, protector.

I read Malwarebytes is good for iMac.

Whats the LATEST, or best, and is there a Apple product.?

Running OS X El Capitan 10.11.6 - iMac 2007