Missing inventory player data

When I try to change my world from a paper world to a vanilla world everything stays the same except for all players not having their personal data. How would I be able to fix this?

Per-player information is stored in the playerdata folder which should be located inside the world folder. (assuming you haven’t changed your world name). There should be a bunch of <uuid>.dat files inside the playerdata folder.

The UUID.dat files are getting transferred over successfully (because they are in the world folder like you mentioned) however, the inventory, end chest, and XP level are not showing up in the world. (Players don’t have their items). Advancements are all up to date (Which I assume id because they are stored in a separate folder)

Hmm, yeah advancements are stored in a different place. Inventory, endchest, exp level, location and whatnot, are in those <uuid>.dat files. Do you have a world container set in bukkit.yml? Or have you changed the world name in server.properties?

I do not have a world container set in bukkit.yml and I also haven’t changed the world name in server.properties.

I am working with Backspace789, here is what we are trying to do. We currently run a paper survival server and we want to switch from paper to fabric in order to run lithium and possibly carpet mod. We want to ensure that we can use our world (and player data) once we switch to fabric. Any suggestions on how to make this happen.
(This is what we have tried thus far: https://www.youtube.com/watch?v=rjIrWTl70nA )