The file extension is just dbc, not dbcs.
Don't copy the DCBackup at all, delete that.
From the DCCache folder just move the dcdb0.dbc file only into the Mods\ Packages folder (or in your case, Mods\ dbcss).
I want to amend what I wrote here; it is best to copy the dcdb0.dbc into the Mods\ Packages folder, not move it. I've been finding that, although Riverview and custom Sims3Packs are showing up okay, any worlds I created with the CAW tool disappear when moving the dcdb0.dbc file. I tried it any way I could (even moving all of the DCCache files) but having two copies seems the only way to have new worlds as well as custom Sims3Packs.Don't copy the DCBackup at all, delete that.
From the DCCache folder just move the dcdb0.dbc file only into the Mods\ Packages folder (or in your case, Mods\ dbcss).
I had to actually uninstall and then reinstall my created worlds through launcher to get them to work. Be advised that your dependant saves will be deleted, so move your saves folder first.
I wanted to avoid having two copies of the dcdb0.dbc in game- as the game is surely reading the same information twice. Remember to re-copy the dcdb0.dbc file into Mods when you install future custom Sims3Packs.
Anything you install via the in-game store tool will be installed to the DCCache in Documents, so that's the one to backup.
If anyone has a better method, I'd be interested to know.
When I moved my dcdb0.dbc file into Mods, I wasn't sure which one to put it in...the base game Mods folder or WA? I started with just WA and some of my CC reappeared in-game. I went back and moved all the .dbc files (there was a dcdb1 and dcdb2 as well) and put all the little suckers in both Mods files, base game and WA. And, happily, the vast majority of my CC is back. Everything that originally came from the store - legitimately or otherwise - has been restored. Woohoo! There are a handful of patterns missing and some hairs, as well, but I can live without those for the time being.
I'm not sure if it was placing the files in both Mods folders that did the trick, or if it was adding the additional dbc files, or some combo of both...whatever it was, I'm just very relieved to have my CC back.
Now I'm thinking I should copy the .dbc files back into their original locations, as Simsample suggested, to avoid any problems if I decide to tackle this CAW thingamajigger.
Thanks, everyone, for all the input and assistance!
Edited to fix general typographical retardedness.