I need a backup of the firmware of my board

Hello, i hope somebody can help me. I am new, only a user of the board, and Need a backup. I have a 3D Printer CR-10 with Marlin-Firmware. .

It is the stockrRom, i want to save, to have a backup, if something goes wrong in updating. One board is a Melzi-board, the other i have bought and updatrd the Printer, i dont know.

What doe i Need to make a hex-dump of the Rom? ISP-Adapter ? Can somebody explain me the way step by step, because i am no Computer Freak? Thank you.

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I know, but i need no support for the firmware, but how i read it out from arduino. Because of this circumstance i think i can get help from here, because it is an arduino problem. I need no help to adapt the marlin to my machine, i need a backup, if i flash the new one and get a brick, because i have not the sketch from the file it is on the rom.

Read it out with an ISP programmer using avrdude from the command line - google will get you the documentation for avrdude if it’s not clear from the help, and you can upload a sketch with verbose output enabled to get the command line Arduino IDE invokes to upload code (you don’t even need the board connected - it’ll just error out if it’s not) so you know the path to avrdude and the path to the avrdude.conf file.