Can't "Show Package Contents" with certain file type!

I have some files with the extension .nks, this is a format that only works with the application Kontakt. Kontakt is a music app that plays back samples in an easy way. So there are a lot of audio files in the .nks files that I have, but I don't want to use them with Kontakt. I prefer to take all instrument samples and put them in folders because they are easier to use in every way. Usually I would be able to just right-click and click "show pack contents" but this time that option is not available. I would really appreciate if someone could help me out with extracting those audio files. Thanks!

 

Well when I right-click and select "get info" it shows that the file is not a read only file. I got it from the website soundsonline.com