My younger brother and I bought a new Xbox and I transferred all of our files with a USB flash drive to the new one. I have an Xbox Live account but he doesn't. I was able to recover all of my saved data just fine. My brother can see his file on the new Xbox, but when he tries to access it, none of his achievements seem to be there. Is it because he doesn't have an Xbox Live account? Would it help if he signed up for a month so he could retrieve his data or is it just lost now because he needed to have his own Xbox Live account before we transferred everything?
You should be able to upgrade his account to a free (silver) account, and then recover it to the new console. From there, the achievements should follow the account at that point. You can find what should be a guide here.
However, that said, you should be able to follow this tutorial and get the profile onto the new Xbox without issue. Just transfer it back from you USB onto your new Xbox harddrive.