Hello, welcome to the forum.
First, run MCServer - this will create a default map for the server, in the "world" folder.
Go into the "world" folder and note that there is a "region" subfolder in it.
Take your world that you want to move, and locate its "region" folder.
Copy all files from the original "region" folder into MCS's "region" subfolder.
If your world has Nether and / or End, things will be a bit more complicated. You will need to add a new world to your settings.ini, that will represent the Nether / the End. Then create the folder for that world (same name as in settings.ini), create a world.ini file in it and set the Dimension to Nether or End, then create a region subfolder and finally locate the Nether / End region subfolder of your original world - usually they're in the DIM-1 / DIM1 subfolder. Copy the files from the original region folder to the new region folder, and you're done.
@STR_Warrior I think this is a good candidate for your FAQ.
First, run MCServer - this will create a default map for the server, in the "world" folder.
Go into the "world" folder and note that there is a "region" subfolder in it.
Take your world that you want to move, and locate its "region" folder.
Copy all files from the original "region" folder into MCS's "region" subfolder.
If your world has Nether and / or End, things will be a bit more complicated. You will need to add a new world to your settings.ini, that will represent the Nether / the End. Then create the folder for that world (same name as in settings.ini), create a world.ini file in it and set the Dimension to Nether or End, then create a region subfolder and finally locate the Nether / End region subfolder of your original world - usually they're in the DIM-1 / DIM1 subfolder. Copy the files from the original region folder to the new region folder, and you're done.
@STR_Warrior I think this is a good candidate for your FAQ.