I think so you have been using Lightroom 5 until now, so you may open the Lightroom 5 catalog in Lightroom CC 2015.
And you will get a prompt to upgrade the catalog and you should be good to go.
And- when LR upgradeds a LR-5 catalog to the LR-CC version it may rename it from something like "My Catalog Lightroom-5" to- "My Catalog Lightroom-5-2". "....-5-2" is the LR-CC catalog. You can rename it to something more appropriate if you wish.
Do the backup files have a .ZIP extension or a .lrcat extension? If they are .zip then they are LR CC backup files even if the name includes Lightroom 5.
When you installed LR CC it normally copies and converts the LR 5 catalog to a LR 6 catalog. LR CC also picks up some of the preferences from LR 5. One of those is the location used for the LR backup files. So you could end up with backups from both LR and CC in the same folder.
Ok I see what I have done now Lightroom cc has Lightroom 5 catalog 2-2 lrcat across the top. So how do I get Lightroom cc to give me the prompt and upgrade to change the 5 cat to cc
thanks everyone for your help
It already has. LR CC/6 will not open a LR 5 catalog without first making a copy of the LR 5 catalog and converting that copy to a LR CC/6 catalog.
You didn't bother to answer the question I asked. Do your backups have a .(DOT)ZIP (or .zip) File Extension? If they do then they are LR CC/6 backups.
But you don't need a backup to load the catalog on another computer. Just copy the working catalog file along with the Previews.lrdata folder over to the new computer and if when you install LR if it doesn't auto see that copied catalog you go to File>Open Catalog and point it to the copied over catalog from your older computer.
The back ups are lightroom 5 -2-2.lrcat.zip
Then those are LR CC/6 backups.