Moving a server to be behind BungeeCord, how do I get players to keep their inventories and spawns?

Hello everyone,,

I was previously running a small FTB Builders Paradise server for my family. I'm now trying to put it behind BungeeCord so I can run multiple Minecraft servers and people can connect via subdomains instead of ports.
https://19216801.onl/ https://routerlogin.uno/https://192168ll.link/
I've got this working...

Moving a server to be behind BungeeCord, how do I get players to keep their inventories and spawns?