Uploading only The End dimension to an existing server

Okay, so err... First thing first, we're playing on paper 1.17.1, so the world tab is already divided into 3 sections: world, world_the_nether, and world_the_end.
From my understanding, if I want to upload a world, I could just use the upload button on the world section. But what if I only want to change The End? I can think of 2 ways to do this but I'm not sure which one is correct, or if they're correct at all:
+, Do I need to download world_the_end.zip from the current server, replace the DIM 1 folder in the zip I donwloaded with another DIM 1 of the world that I want, then re-upload it?
+, Or do I just need to click the "Upload" on the world_the_end section, then select my own DIM 1 folder (of the wanted world), and it will still work?

On a side note, The End dimension in the current world we're playing has already been explored (somewhat), so it's about 147mb, and the one I want to replace with is unexplored, so it's only about 20mb, so I'm not even sure if it'll work properly. I feel really risky just looing at the size, honestly.

Quote from Hilex_23

This one.

The size shouldn't be a problem but you can always download the current end dimension as a backup if you're worried.

Thank you! I'll make a backup first, then try it out.