Although .dmg is a macOS disk format, there are a number reasons of why you'd want open them on Windows computers. Here's how to get started.

On Windows, HFS+ can be read only with the aid of software such as MacDrive or MacOpener; it's possible to run MacOS 8.1 in emulation, but I know of no suitably old software that can open .dmg ...

If you want to convert an Apple Disk Image (DMG) file to ISO format on Windows PC, you can use the command prompt or free AnyToISO tool.