To make things simple what you can do is to first move your current catalog( which is one of your back up file) from the back up folder.
- Create a new folder name Lightroom Real catalog and transfer the following files for the backup catalog you are working on:
2.Backup catalog Previews.lrdata
3.Backup catalog Smart Previews.lrdata
- Once you moved it to new location then launch the .lrcat file with Lightroom CC 2015, It will then ask you to upgrade it and will generate an upgraded catalog for the same.
- You can rename your Catalog as well before launching it
- Check the following link to know about how to move a catalog and how to rename it: https://helpx.adobe.com/lightroom/kb/catalog-faq-lightroom.html
Worked like a charm, thank you!
Glad to help