Hey!
There is no need for a plugin! Either navigate to your Server dashboard and just put on the latest save. No need to worry if you haven't backed up your world, the server does it automatically! Once you are in the server Dashboard go to Backups and search for Restore Server. This will then put on the latest save, just give it a few minutes!
In case this doesn't work, try to Repair the server files! You can do this via the Server Dashboard in the Danger Zone. Simply click the Repair Files button and wait a few minutes!
Good luck! Let me know if that helped!