Every datapack and resource pack needs a pack.mcmeta file in its root, with a pack_format number Minecraft uses to decide whether the pack matches your game version. Pick a pack type and version below to get the correct number filled in automatically.
pack_format numbers differ between datapacks and resource packs for every version from 1.20.3 onward — this tool tracks both tables separately so the number is always right for the pack type you picked.