Problem: Atmega16u2 firmware, MEGA2560 r3

I guys, I have one new application and I need to burn a new Chip “Atmel”. I have bought it virgin, in digikey. But the I have not get that my computer read my new Chip as “Arduino Mega 2560”

DO you know what is the correct file .hex (firmware) to program one Atmega16u2 (virgin), inside MEGA2560??? I have been testing different files without successful. All is inside these chapters:

C:\Program Files (x86)\Arduino\hardware\arduino\avr\firmwares\atmegaxxu2

C:\Program Files (x86)\Arduino\hardware\arduino\avr\firmwares\atmegaxxu2\arduino-usbserial

otherwise, I have been testing with another .hex but, at the moment I have only get one “unknown file” in the “Device manager”. It not appear in my IDE of Arduino, or it appear as you can see in the .img.

I have been trying to check the firmware file with Flip from Atmel, but I have not yet the signature bytes and is not possible to upload the .hex to the microcontroller, for my new atmega16u2; i only get: “Could no write to the USB device”