Export S Notes as text files
If you are looking for a way to export just the text (and save it as .txt) from older Galaxy S Note notes (.snb), the best way would be to download the S Note for desktop from Samsung website and use it to export SNB to PDF (you need to first import the *.snb file via the File ► Import ► S Note files function). When you have the *.pdf file you can use some of the existing PDF to TXT conversion solutions to get the plain text file, or you could simply copy paste the text out.
Converting Shanda Bambooks to text files
Use Calibre to Shanda Bambook eBook files (.snb) to Simple text file format (.txt). Open SNB file in the Calibre ► Click on Convert books button ► Select TXT as output format ► Click on Ok button.