You must reinstall Windows 10 using a Legacy/BIOS method. Avoid selecting the "EFI Boot" option (the one with the orange icon) during the installation process. Use a USB 2.0 drive if possible, as USB 3.0 drives sometimes fail to trigger the Legacy installer on 2012 models. 🔊 Driver Information
If you are already in Legacy mode but still lack sound, you may need to manually point Windows to the correct drivers: macbook pro 2012 audio driver windows 10 hot