Did you backup the server?
If so you can restore it.
I sadly did not no. I wish I did, but I didn't think that changing software would erase everything I've built so far. So that means I can't? 
Posts by Baguccito
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Hello! I have recently installed Forge and Worldedit, and added them to my Aternos server. Before the software and mod were added, I had built a few things already. It took me days to weeks to build, and I definitely wouldn't want to lose these. Guess what happened, after I installed Forge and Worldedit the builds I made were completely gone. However, everything was the same before I built anything. Biomes were the same, a river on the same place, etc. World same, but the builds I made were completely gone. Are these still stored somewhere in my World files, or are they completely gone? And if they still exist, how do I find them and upload/restore them again? Thank you in advance.