Xiaomi Redmi update with MiFlash required downloaded official firmware and MiFlash, install it on PC and unpack firmware, run MiFlash and follow this guide.
If you want to flash stock firmware for Xiaomi Redmi using Fastboot – download and unpack ADB&Fastboot, install Drivers. How to flash stock firmware Xiaomi Redmi using Fastboot instruction is here (you need to unlock the Xiaomi bootloader).
If your model is not present, you can write a comment below. We’ll solve a problem and give a link for update firmware.