Minecraft 1.12 Multiplayer world to singleplayer [duplicate]

Provided you're copying the world folder, your player position should be in the same location. Go into the file once you've pasted it and check in the following directory:

C:\...\.minecraft\saves\<world name>\playerdata

In there should be a .DAT file with your UUID on it (you can find your UUID on this website). If there is not a .DAT file with your UUID on it then it means that either for whatever reason you don't have a .DAT file for that world, or your server has stored it somewhere else. Try looking elsewhere in your server files for a .DAT file with your UUID (or possibly even IGN) on it.

Moving the .DAT file into the file path for your world mentioned above should update your inventory, location and such.