1. Your host OS is Windows, not Linux, and ... well, this is a forum for Linux issues, not Windows'.
2. Last I checked, VBox can't download(as in download from the internet)iso files.
3. Your issue is that the Ubuntu VM can't run for some reason in Windows 10. It has nothing to do with Linux/Ubuntu, but rather something's not working as intended in your setup; Windows 10 + Virtualbox.
4. I suggest you go here https://forums.virtualbox.org/viewforum.php?f=6&sid=024dfe9e6b4b27d2806ccfcf4385e61b and post your issue over there.
5. Ask in a Windows' forum like this one https://answers.microsoft.com/en-us/ or this one https://windowsforum.com/
Start your computer, enter BIOS, and enable virtualization. Try that first. It tells you in the error message that that's the current problem that's stopping you. (There may be other problems after that, but start with that one.)