Collections in Bridge CC - Locating the files to allow the collections to be backed up

For my Windows 7 system, I have seen a number of posts indicating that collections files are located in

C:\Users\<user-name>\AppData\Roaming\Adobe\Bridge CC 2017\Collections

Indeed, I have files named <collection -name>.collection in that folder, however, they are just small (1KB) files which contain the parameters used to define each smart collection.  They do not include pointers to the images. 

Where are the files with the information as to which image is included in each collection?

Thanks in advance for any assistance.