Ah, you're using file.io
I'd reccomend you to use dropbox. If you are willing to retry with dropbox, here's a quick tutorial.
Go to dropbox.com, and make an account if needed.
Drag the world file into the blank space, and once it's done uploading you should see a popup at the bottom confirming the upload.
Find it on the list, and hit "Share"
At the bottom of the new popup window, create a link, and copy it. Go onto your minehut server.
Do /ul world (world_name) (link)
Don't hit Enter yet, change the "dl=0" at the very end of the link to a "dl=1"
Confirm the command, restart your server, and join it using /world.