For those who dont kow how to here you go:
Step OneGo into ur server properties file (Right click+open with+Notepad or preferred text editor) and make sure level name is changed to the name of ur save
ex. World1,World2,World3,ect
#Minecraft server properties
#Sat Jan 22 11:15:05 EST 2011
server-ip=xxx.xxx.x.xxx
server-port=25565
level-name=World1
The folder where your server files will be wherever you put and first ran the server at (On windows anyway). So just find "minecraft_server.exe" and that is where your server dir is.
Step TwoGo into your minecraft single player folder for me its C:\Users\Administrator\AppData\Roaming\.minecraft\ saves (might be different)
and take the world folder that you want, right click - copy
Step Threego into your server folder for me itsC:\Users\Administrator\Desktop\Smp_Server (will be different its ur server folder)
right click and paste away.
The folder where your server files will be wherever you put and first ran the server at (On windows anyway). So just find "minecraft_server.exe" and that is where your server dir is.