You can use iCloud or iTunes to restore iPod touch from a backup.
Restore from an iCloud backup. Reset iPod touch to erase all settings and information, then sign in to iCloud and choose “Restore from a Backup” in the Setup Assistant. See Restart or reset iPod touch.
Restore from an iTunes backup. Connect iPod touch to the computer you normally sync with, select iPod touch in the iTunes window, then click Restore in the Summary pane.
When the iPod touch software is restored, you can either set it up as a new iPod touch, or restore your music, videos, app data, and other content from a backup.
For more information about restoring iPod touch software, see support.apple.com/kb/HT1414.