Instructions
Turn on the Xbox 360 console and insert the flash drive into one of the game controller's USB ports.
Select the "My Xbox" dashboard, and then browse to "System Settings."
Select "Memory" followed by "All Devices" from the subsequent menu.
Select the "Games" directory, followed by the saved file you wish to back up. Full games as well as saved files are shown; select items that are labeled "Saved Game."
Select "Copy" from the file's options displayed, followed by the flash drive currently connected to the console. Allow the saved file to successfully transfer to the device, which may take several minutes.