how do I know if I am paying for more storage?

See the following from Manage your iCloud storage - Apple Support (and look at the "nnGB of nnGB Used" number. if the last number is more than the free 5GB then you have an upgraded storage plan)

See how much iCloud storage you're using

Your iCloud storage is different from the storage capacity that comes with your device. Learn the difference between storage on your device and in iCloud. 

On your iPhone, iPad, or iPod touch

Go to Settings > [your name] > iCloud. To see more detailed information about how apps and services are using your storage, tap iCloud Storage or Manage Storage.

On your Mac

Go to Apple menu  > System Preferences > Apple ID > iCloud. To see more detailed information about how apps and services are using your storage, click Manage.

On your PC

Open iCloud for Windows.

On the web

On a supported browser, sign in to iCloud.com, then click Account Settings.

Go to System Preferences/iCloud (Apple ID for Catalina or later) and see how much storage shows there. On a device, go to Settings/Your Name/iCloud to check.