Greetings fishergirls,
Welcome to the Apple Support Communities!
I understand that you would like to transfer purchased content off of your iPod to the iTunes library on your computer. It sounds to me like you are attempting to transferring purchases correctly, but nothing is happening. To ensure; however, that you are working through the correct steps, please review the attached article.
Redownload or transfer your iTunes Store purchases from an iPhone, iPad or iPod to a computer - Apple Support
If transferring your iTunes purchased content appears to still not be working as you would expect, you may consider downloading off of your purchases directly to your iTunes library. You can do this by following the steps in the next attached article.
Download past purchases from iTunes - Apple Support
Cheers