Hello,
In my last message I gave that output that I saw and mentioned that it showed 36.3. Before attempting anything else, I just wanted to make sure that I could boot up Jetpack 6.0. However when I booted up the device with an sd card that was flashed with JP6, it now showed the version 5.0-35550185. According to this post it meant that I had successfully downgraded to the correct UEFI version needed for Jetpack 5.1.3. So I reflashed my sd card with jetpack 5.1.3 and it worked! I am now able to use my Jetson Orin Nano with that jetpack version.
Thank you for you help