Changing an existing world

So my wife and my kids and I recently started playing valheim together. I was able to set it up on my home server. In fact I have two worlds running on there. The issue that I'm running into though is that our primary world that we've been playing in is a straight vanilla world. I'd like to change the drop rate in the world without changing any other modifiers. When I exported it and started it in my personal rig. I changed the modifier. However when I exported it back into the server. It hadn't changed.

I'm not sure if I didn't grab all the needed files or what but could someone please explain which files I need to grab to mod this and return it back to our server?

Thanks in advance.