This article will describe how to add your single player world to your Minecraft server. It will describe the best practices to follow to avoid unnecessary issues. Within this article, it will be using and FTP Client like FileZilla or WinSCP to upload your files. See connecting to your server via FTP to learn how to do this. (Make sure your server is stopped before uploading)
Make sure you have your versions are the same within your Minecraft server and your singleplayer world. If you are using different versions, in some cases this may work though it isn’t recommended, it is always suggested that you have a copy of your world. Just know the version you started the Minecraft Server in, and what version of the server jar you are running.
Once you understand if your server is on the correct version, on your windows computer, do the windows shortcut Win+R and type “%appdata%/roaming” without the quotations. This will show locations of various files, and at or near the top you will see “.minecraft”. Alternatively, MacOS and Linux has the .minecraft folder located within the /home/’username’ directory. Make sure you are viewing hidden files (In most cases this can be done by Ctrl+H or within your file explorer preferences)
Open up the .minecraft folder and you will see a sub-folder named “saves” within that folder you will see a folder with the name of your world.
Uploading the file via an FTP client. To do this once you know the location of your folder, connect with your FTP client and upload the world to the Root Directory of your server ‘/’. This is the main directory you will see when you’re connected. To do this you can either click and drag the folder into the FTP connection, or you can find the location in the pane on the left. Either way it will create a copy and upload it to the server.
Open the World you just uploaded, make sure this is done on the new folder that showed up in your server side of the FTP client. Then delete the subfolder named “playerdata”, this will ensure you don’t run into issues with that folder once it’s loaded.
Change the name of the world to the name you have specified in your server.properties, if you haven’t edited the name in the server.properties, then the default name is “world” without the quotations.
Start up the server and join it, if you have done everything correctly you will be placed in your singleplayer world within your server, and it has turned into multiplayer.