Hi I’m unable to cancel my Dropbox subscription because it doesn’t show up in my settings

Did you subscribe with Dropbox directly?

Use this shortcut to jump to the section about what to do if you can’t find the subscription that you want to cancel. --> If you want to cancel a subscription from Apple - Apple Support

If you still can't find a subscription, contact Apple Support using this issue-specific link at the end of the section. --> https://getsupport.apple.com/?caller=kbase&PGF=PGF63006&category_id=SC0060&symptom_id=23208

Is it possible that you subscribed directly through their website and not through an App? You may need to log into their website and modify your subscription on your account that way.