I have assumed you are looking for a guide that addresses the "file" as a permission file (.bin) rather than a hacked tool, as Xiaomi’s official method requires an unlock file. Title: The Redmi 6 Pro Bootloader Unlock Guide: Do You Really Need a "File"? TL;DR: Xiaomi no longer issues official unlock permissions for the Redmi 6 Pro. If you are searching for a "file" to unlock it today, you are likely looking at unofficial deep-flash engineering (EDL) methods or unofficial patched binaries.