You need to create the config/copy folder yourself or the mod won't work!
Would be pointless using it if you don't put stuff in the folder anyway xD
This mod allows you to have a folder which can be used to keep the contents of a world up to date. It will copy the contents of everything in /config/copy to any new world that is created. It will also update the contents in each world to what's in that folder, allowing you to make changes in the future. Its main purpose was to allow you to have customnpc data in each world for any packs. You can also use it to copy over datapacks as long as you create the folder /config/copy/datapacks and place them in there then they will be loaded early enough for worldgen etc.
tldr; An easy way for pack makers to have default datapacks as well as allowing for copying of other per world files where needed.