The file you want to upload is the .cgz file (and the .cfg, if you have one). The .BAK will work if people rename it to .cgz, but it won't be the right version of your map.
EDIT: woops, didn't see that you had uploaded the .cgz. You don't need the .bak
EDIT: woops, didn't see that you had uploaded the .cgz. You don't need the .bak