how to disable secure boot if its not in bios?

I'm trying to install Linux Mint on an old HP notebook. I plug in the USB and go through the installation process, but after it finishes and prompts me to reboot, I get a message saying that no operating system can be found.

I looked online and people suggested to turn of secure boot in bios, but I cant find the option there.

Does anyone have an idea how to fix this?