I'm slightly confused, are you the owner of the Aternos server?
Do you have access to the owner's account?
If you have access to the account, go into the "world" section in the server page, and download the world.
Just replace the level.dat in the server with the one from the Aternos files, and any player data you want. If you don't know what I'm talking about, I'm afraid I can't help.