Try using Kindle Mate. This is computer software. Just download and install it, plug your Kindle into the usb port of your pc/mac and your highlights and notes will be copied over into the software.
Unfortunately, the official website is all in Chinese, but this is the download page from the site:
http://kmate.me/download/
You might find this useful too:
http://kmate.me/demo/
And there must be youtube vids relating to the software somewhere.