BIOS cannot find a stick

Hello!! i am trying to install windows 10 on a assembled pc. The problem is that I find myself in a paradoxical situation: the BIOS sees me the key only if formatted in GPT format, however it warns me that it cannot be used because "This drive can only boot in UEFI mode. It can not boot in BIOS / Legacy mode. ". He tells me to redo the key in MBR format, but when I do this I can't find it anymore at startup.