Actually, you probably don't actually “own” any fonts unless you commissioned someone to design a font for you and transfer all rights to you. All you typically “own” are licenses to use particular fonts.
You don't indicate why you need to “download” such fonts. Presumably, you had a system / disk crash and are unable to retrieve the fonts from the crashed system / disk; is that the scenario? In such cases, the best solution is to retrieve the font files from system backups that you have diligently been performing. The big problem is if you haven't been backing up your system and thus cannot simply access those font files from your backup! Ouch!
You don't indicate from whom you licensed the fonts. Thus, a general response won't suffice. Depending upon the font vendor and whatever documentation you have of your license purchase, the font vendor's support organization may be willing to make an additional copy of the font files available to you, whether by download or otherwise. Your best bet would be to contact the support organization of the font vendors you licensed the fonts from an see how they might accommodate you.
PS: This is type of situation makes a great case for the discipline of frequent system backups. Also, services such as Adobe's Typekit with font repositories in the Creative Cloud which automatically synchronize with your system would definitely resolve this form of problem.
- Dov Isaacs, former Adobe Principal Scientist (April 30, 1990 - May 30, 2021)