Adb Platform-tools ((top))
You are either not in the correct directory in your terminal, or you have not added the folder to your System Path variables. Navigate to the folder using cd commands (e.g., cd C:\platform-tools ) and try again.
While ADB works when the Android OS is running, works when the device is in the bootloader mode. This is critical for low-level modifications. adb platform-tools
Unzip the downloaded folder to an easy-to-access location, such as C:\adb on Windows. You are either not in the correct directory