Extracting Audio from Pro Res files?

In an effort to free up some space on my hard drive, I was thinking about exporting some of my CRI files into ProRes files. Some of these CRI files have a narrow optical audio track. Will I be able to extract the audio from the ProRes files or does this have to be done from the CRI files.

Any other recommendations for shrinking down these CRI files to save some hard drive space?