how do you find out how much storage you have on icloud

See the article Check your iCloud storage on iCloud.com - Apple Support

Hello

you can find out how much storage you have by going to Settings > Tap your name, under Subscriptions you will see ICloud and it shows how much. I have 200GB. Hitting that > arrow will show you more information. Backups, photos, Messages, others and how much of ICloud , in my case of 200GB has been used.

hope that helps