In order o export your data select the settings gear - exports/backups - choose content (I chose HTML) and file type (ZIP) - export
You will receive an email when the export is ready to go. When I downloaded the file and opened the ZIP file, it is important to know that there are now style customizations (so it will look different).
Wikispaces created a nice set of directions to follow (in their support center) - http://helpcenter.wikispaces.com/customer/en/portal/articles/2920537-classroom-and-free-wikis
Embedded below is a 1 minute and 17 second YouTube tutorial I created.