Do you have a FireWire HDD drive which you can setup as a bootable disk?
You also need to work with the OS this system supports the highest is macOS High Sierra (10.13.6)
You can get it from here [https://support.apple.com/en-us/HT211683|How to get old versions of macOS]. then follow this guide to convert it to a bootable file when you have copied it on your FireWire drive, but you do need to format the drive to GUID and a Journaled file system. Follow this guide to convert it [https://support.apple.com/en-us/HT201372|How to create a bootable installer for macOS].