Welcome to the Community, @alishacomer! Hope you’re well.
Can you clarify what you mean when saying the files don't show up on your iPhone, unless you use the Upload button?
If you go to your Dropbox account online, do you see the same files that appear in your File Explorer > Dropbox?
If not, I'd like to know the syncing status and app version of your desktop app.
Let me know what you find.