If you actually have backed up your data to the USB disk, then you simply need to mount it and copy the files to wherever you want them, e.g.
First mount the device on /mnt/tmp. Obviously this assumes that the device you want to mount is /dev/sdb5. You'll have to make sure, though..
mount /dev/sdb5 /mnt/tmp
Now copy all the files (and directories, recursively) in /mnt/tmp (i.e. those that are on #the USB disk) to your home # directory. Obviously, this assumes that your home directory is /home/stuff, so modify as appropriate.
cp -R /mnt/tmp/* /home/stuff
Read the man pages for mount and cp if you need more information about those commands. Please note that these are only examples and you should read the aforementioned man pages, or ask for more information if you need it (so that you understand what the commands do and don't make a mess of anything).