Emulate a USB Storage

Hello, i want to make my Arduino Uno/Mega to appear as an USB Device. How can i do that?

Zipfel1

How can i do that?

With a soldering iron and a fair degree of skill. The Mega does not use the same kind of serial-to-USB chip as the Micro and Leonardo. You'd need to change chips, to the one that the Micro/Leonardo uses. Good luck with that.

It is already a USB device. It implements the Serial interface.

You're probably looking for the Mass-Storage interface. That won't work with a Mega. It makes no sense. It's like asking a car to implement the "drive on train tracks" interface.