Want to change server to Vanilla from Forge

I tried solving this issue earlier by downloading the world, changing the software and re-uploading the world but it does not work. I read something about changing the server software in the world folder in one of the threads; however, I don't know how to do it exactly. I don't want to lose my world but I need to change it back to Vanilla any help?

NOTE: I have installed three mods, namely, Building Gadgets, WorldEdit and WorldEditCUI

Quote from Toothy

You can just install Forge, it won't delete anything and the world will stay

Still always have backups tho

It already is Forge. I want to change it back to Vanilla.

Quote from Toothy

Oh nvm I read the title wrong - all you need to do then is download your world (not backup, download it from https://aternos.org/worlds), install vanilla, and upload it on that same page. That will (or should) preserve everything

I did that but the upload always fails though.... The world doesn't change. To see if it was an issue with just my server, I tried it on my friend's server but that did not work either.

Actually this time the error did not happen😅😅😅I suppose the problem is solved... I am sorry to disturb you but thanks for helping😄😄