The Resource Pack required on each client running Demons and Dreams can be found here. For the Data Pack, see https://www.curseforge.com/minecraft/texture-packs/demons-and-dreams-datapack
This Resource Pack primarily affects only items marked with the CustomModelData NBT data. The only items that have been retextured without use of this NBT are chainmail, which has become holy armor, structure voids, which are now Ender Tables, and the full moon, which is now red.
Demons and Dreams is a content datapack that this resource pack is made to work with. If the datapack is installed, this resource pack provides all custom textures and item names (English only). It serves no purpose on its own.