https://serverlist101.com/news/minecraft-1-16-3/ - Your multicraft management panel has a tab in the left hand menu called config recordsdata. The very first you OP anybody on a multicraft management panel you'll need to use the control panels console. Similar to mods, you might want to log into FTP to upload a large folder like a world. All you could do is stop your server, log into Filezilla, drag your world folder into it, save and restart your server. If your world folder has a customized title then you might want to set it in your control panel on the WORLD setting in your management panel ...