I just purchased a ds218+ and would like to use it as channels dvr. I also would like to move my existing library to it. I've never had a NAS, so I'm a bit clueless. My current set up is channels dvr running on a raspberry pi with recordings stored on a WD passport USB drive. I have heard there are a lot of you using the ds218+ I was hoping someone would be kind enough to walk me through what I need to do to move the existing content and set it up. I've been looking through old posts, but have not found anything that is explained as simply as I need it. 
I use an Apple tv for watching. If that matters
Move the DVR folder to the NAS.
Install the DVR Synology package, then open http://x.x.x.x:8089/restore using the IP of your NAS
Thanks. That seems fairly simple. My biggest problem is moving the dvr folder. I tried to drag and drop the folder. It copied the folders names over but none of the media files. I've since been using the upload feature on the NAS to copy over the media files one folder at a time. It is taking forever. I was wondering if someone out there has a suggestion to move the whole folder
Can you elaborate on the “drag and drop” you tried? Did you do that from the Pi UI? And if so, to what, a SMB share on the NAS?
I plugged the USB drive that had my DVR files into my laptop on the same network. The folder was there. I had a folder open on the NAS. I just did a simple right click and dragged the file from the USB drive to the folder on the NAS
Just tried to install the DVR on my NAS. It did not work. Got the following message

At this point. I'm not too worried about the old files. I would like to get the dvr working on the new NAS. That's why I bought it.
Your dns Network Settings on the NAS are incorrect
You need to go to the Control Panel and check your network settings. It should be located at "Control Panel -> Network -> Network Interface", click the one that says "Connected", and then click "Edit" and go to IPv4 and IPv6 and make sure your DNS settings are in there right.
Or if you're good with CLI just ssh in and run 'cat /etc/resolv.conf' and make sure the nameservers are correct.
Up and running. Thank you to all who replied
this was dated December 2018 - Is this information still valid or is there a new way? thanks