my custom world from planetminecraft not appearing in my generated world

Hello! im trying to import a world i downloaded from planetminecraft to a world i generated using multiverse plugin but the custom world is not imported in the generated world as i tried multiple times uploading it in the aternos 'worlds' section. pls help

no but ill try that

one world i imported worked but when i tried to import it to a multiverse generated world, its not there