Editing the data file in your world save

I'm trying to install a datapack for a server that has been running for a while. The datapack (specifically this one http://www.9minecraft.net/ship-out-on-the-oceans-data-pack/ ) has custom maps that need to be placed in the " data " folder in the world folder. The problem is that on Aternos you can't import files to the data folder. I've tried downloading the world, putting it in myself and trying to re-upload, but because of how much we've played on it the file is over a gig and cannot be uploaded. Any advice would help, thanks.