Some motherboards may have “jumpers” (small metal pins embedded on the board) that you can use to clear BIOS/UEFI settings and return them to their factory default settings. The motherboard documentation should have procedures to follow on how to clear BIOS/UEFI passwords.
If the brand and model of the motherboard are hard to find on the board itself, see if you can use the System Information utility (msinfo32.exe) utility in Windows to find them. They will be labeled as “System Manufacturer” and “System Model” in the window of the utility.
A search of the motherboard manufacturer’s website should yield a manual with details on how to clear BIOS/UEFI passwords and other settings, if the motherboards support this feature.