There are several ways of doing this. Have a look at this useful information with video about restoring from a backup or restoring to a previous version.
I am assuming that they are still not in your recycle bin.
This thread is now locked and can not be replied to.
1995-2015: How technology has changed the world in 20 years
Get $800 of free online Nuke and VRay rendering from Google Zync
iPhone 6S preview: What to expect from Apple's next iPhone
Synology invite you to their launch event on 16th September 2015. See the unveiling of the new DSM and products live, plus a chance to win a populated NAS! Tickets are free and available now. Click HERE for more details