While Apple no longer sells Mac OS 8.6, it is still technically proprietary software. Most users find these ISOs on "Abandonware" sites. To ensure you’re getting a safe file:

To run the ISO, the emulator needs a "BIOS" (the Mac ROM). You’ll typically need a "New World" ROM for 8.6.

Essential for mouse and keyboard input in emulators.

This is the gold standard for emulating Mac OS 7.5 through 9.0.4.

Since you likely don't have a PowerPC Macintosh G3 sitting on your desk, you’ll need an emulator. Here is the standard workflow:

It handled multitasking much better than OS 8.1 or 8.5.

In the SheepShaver GUI, add your "Mac OS 86 ISO" to the volumes list. Ensure it is at the top of the list so the emulator boots from the disk image rather than an empty virtual hard drive.

The image must contain the proper partition map to be recognized as a startup disk.

This query is a bit of a mix—were you specifically looking for the for emulation, or are you trying to find a Hackintosh (x86) build for a modern PC?