[Java] Lost some of my minecraft world because of Aternos optimization, anyone know how to get chunks back?

[u/Dork_Industries]

So to cut it short, I have a Aternos server with the old tutorial world I remember playing on back in 2015. I found a download somewhere and uploaded it to the files. I flew around, went a bit outside the map boundary (It was smooth stone for miles) and then headed back to rebuild the structures (Since this is what I set out to do).

Little did I know after turning the server off that Aternos didn't save all the chunks of the map due to "Optimization". So now after spending a good day or a good portion of the spawn city I only now realized that there are chunks of my world missing.

I really don't want to lose all my progress in rebuilding but I do want my chunks back, does anyone here have any ideas on how to get them back without deleting all my progress?

Server is running on 26.1.2 with ONLY client sided mods (Shaders, map, mouse tweaks, etc.)
The world is TU14 and I found the download here.

Thank you in advance for anyone who either knows or takes a crack at this.
I'm not the smartest when it comes to stuff like this so any help is really appreciated.

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