If you search Google for "Fire OS ISO," you will likely find links on suspicious file-hosting sites claiming to offer FireOS_7.iso or similar.
If you need to run Fire OS on a computer for testing, you do not use an ISO. Instead, use the Android SDK Fire TV Emulator fire os iso download
There is no official Fire OS ISO file available for download If you search Google for "Fire OS ISO,"
If you need to restore or update an Amazon device, you can download the latest firmware directly from Amazon's Device Support page . .bin fire os iso download