Instructions
Verify that your flash drive will be sufficient to store your game or games. The drive will have to connect via USB to properly interface with the Xbox 360 and should be a USB 2.0 drive because they are faster than standard USB flash drives. This is particularly important if you are going to be transferring a large amount of data from your system's drive to the flash drive.
Plug in your flash drive to your console. There are USB points in the front and in the back of the console. There is no formatting required to get your new drive ready to work with the Xbox.
Select "My Xbox" from the Xbox 360 menu. Select "System Settings" and then select "Memory."
Select your internal Xbox 360 hard drive and the items that you want to copy from it. Select "Copy." You will be prompted to select where you want the data to be copied to; select your flash drive. This will begin the process of copying all the selected items from your console to your storage medium.
Allow the transfer to complete uninterrupted. Any interruption of the transfer can result in lost data. When the transfer has been finished you should be able to see that the data in question is now being stored on your flash drive.