Trying to create a superflat dimension

Hi i'm trying to add a dimension in my modded server (Big chad guys+) and i've heard that I can do that with datapacks. I tried one on modrinth and also tried to make my own on misode but whenever i check /datapack list it doesnt appear and i cant find it in the /execute command. I'm currently just testing in a singleplayer instance and honestly i'm very lost cause I cant find a straightforward answer online on how to go about getting it to work. I'm running version 1.20.1 and have tried just straight up putting the .json in the datapacks folder of my world which is probably wrong and also looking at how it was done by the one from modrinth with the folders and whatnot but failed to replicate it. 
Any help would be greatly appreciated!
Oh yeah and the purpose for this new superflat dimension is to host events in the server i'm running by importing a hunger games map using worldedit into it (another problem i'll hafta solve but i'm sure i can do it ^^)