Where can I download an image file of High Sierra?
I am using High Sierra and have some 32-bit apps that I need to keep. I understand that I could install High Sierra as a virtual machine using Parallels (which I already have for Windows 10). Then I could upgrade to Catalina and use the High Sierra virtual machine when I need to use the 32-bit apps. My question is, what files do I need to have available after I decide to move to Catalina? Is there a single file that I could keep that would allow me to install High Sierra in Parallels?