Instructions
Insert the USB flash drive into the USB port on the front of the Xbox 360.
Select "My Xbox" from the main menu of the Xbox 360. Select "System Settings." Select "Memory."
Select "Hard Drive."
Select the content you will migrate to your USB flash drive. Select either "Copy" or "Move."
Select "USB Flash Drive." The content will be migrated.
Repeat the steps to place the content on the destination Xbox 360. The only difference is that you will select "USB Flash Drive" for Step 3 and "Hard Drive" for Step 5 to migrate it to the new Xbox 360.