Generally if you didn't do anything special, they are most likely project files.
To create a bundle file you need to do a "save as" and specify the bundle (.cwb) format.
One easy way to tell is to go into Windows Explorer and do a search on all hard drives for *.cwb. If it doesn't find anything, you don't have any bundle files.
The major difference between a bundle file and a project file is that the bundle contains the audio, whereas the project file only contains "pointers" to where the audio is located. If you were to make a copy of a project file and load it on another machine, you would have no actual audio. Whereas, if you made a copy of a bundle file and loaded it on another machine, you would have your complete song (including audio).
For that reason, when making a backup, you should use the bundle format.
As I suggested to you, I would make a backup of all my Sonar songs in bundle format and drop them on a CD (assuming you have a CD burner). Then delete the project files as I described.