If you have searched for "Download Palo Alto ISO Image," you likely need the software. Unlike a physical hardware firewall (PA-220, PA-850, etc.) which comes with firmware pre-installed, the virtual firewall requires a bootable ISO or a virtual appliance (OVA/PAK) file.
Once you have your credentials ready, follow these steps to locate the base images: Download Palo Alto Iso Image
The software list defaults to "Panorama" or "PAN-OS." If you have searched for "Download Palo Alto
You will be prompted to verify that you are not downloading encryption technology to a restricted country. Check the box and click "Confirm." The download will begin. etc.) which comes with firmware pre-installed
Install the VM-Series Firewall Using an ISO - Palo Alto Networks