Hello, I have an iMac running OS X El Capitan (v. 10.11.6). I cannot upgrade this OS according to Apple (due to the age of the iMac), and I cannot use a different computer at this point. Which version of Parallels Desktop for Mac should I use, and how do I acquire it? I saw that maybe v14 would work, but I can't see how to acquire it. I see that the new v16 of Parallels is not compatible with El Capitan. Thanks.