Sync Local Folder with NAS storage device
I would recommend that you look into using rsync. This is a very powerful and widely used backup tool that is included in OSX. You control it via the terminal, or via a script. Meaning that it can be scheduled to run backups at certain times or manually when you invoke it.

The prerequisite is that your NAS has an rsync server daemon running on it.

The beauty of rsync is that you can tell it to incrementally update files - that is, it will only upload files that are new, or have changed. (It can even upload the bits of existing files that have changed). It's very quick and efficient.

Check that your NAS supports rsync and then read into it, rsync is a large topic to cover here but I highly recommend it!

Typically, you'll run the command like this:

rsync [options] source destination


Check this page out for some good explanation and usage examples.