Included in this download is the Level.dat file (mandatory), a single world chunk, and a link to an external MediaFire download. Curseforge enforces a strict 2 gigabyte upload limit, so an external download is necessary.

Curseforge page:
https://legacy.curseforge.com/minecraft/worlds/genstructuresimproved-lotr

MediaFire info page link:
https://www.mediafire.com/file/qr86rna6jv0lwcb/GenStructuresImprovedV1b.zip/file

When the file is downloaded, extract and replace existing world files included in this folder.