There are some cases where you need to create a new world or delete your world due to bugs developing in them that cause lag or crashes. Minecraft servers generate the world folder in the main directory of the server by default. The world folder is based directly on what your "world" value is set to in your game panel (blank by default).We'll go over how to do both:
Deleting Your World:
By default, your world folder will be named "world" and you'll have around 2 other folders also with the "world" name in it such as "world_nether" and "world_the_end" which are automatically generated with your main "world." To delete your world, you simply have to delete all three folders using the built in File Manager on the Control Panel or an FTP program. Once deleted, start up your server and it will generate the new world folders.
Creating a New World:
Instead of deleting your old world, you can simply generate a new one. There are two ways of going about this - either rename your old "world" files to something else and restart or just generate a new one entirely. To generate a new world, log into the Control Panel > Server Properties, find the section "level name" and enter the new name of your world inside the text box.
Then hit save and then restart your server, the server will then regenerate a new map.
Here is a picture to help: