What is your motherboard model?
You need to select the UEFI boot mode in BIOS.
I don't understand why you are trying to boot into Legacy mode.
I don't know which is faster for you: configure the system again or deal with boot modes
Unfortunately some motherboards don't support UEFI bios mode, if that's the case here OP must reload the OS with legacy bios mode which is changing the Rufus software settings to MBR, I have deal with this type of problem once, I'm sure it will work