Can I delete photos that are stored on my I cloud storage

If you use iCloud Photos and you delete them from your phone, you delete them from iCloud as well. iCloud is a syncing service, it is not off device storage.

This is copied from the support article linked below.

What happens when you edit or delete photos

When you edit or delete photos or videos, the changes are reflected across all of your devices.

Edits show up on all of your devices

When you make edits in the Photos app on your iPhone, iPad, or iPod touch or on your Mac, the photo automatically updates across all your devices, including your Apple TV. So when you crop or enhance a photo from your iPhone, you see the changes when you access your library from your Mac. Your original photos and videos are stored in iCloud and you can go back to them at any time, and revert any changes you made.

Photos delete from all of your devices

When you delete photos and videos on one device, they're deleted everywhere that you use iCloud Photos. If you delete something accidentally, you can recovery it in the Recently Deleted folder for 30 days. After that, it's deleted permanently. 

Set up and use iCloud Photos - Apple Support

Mshair10 Said:

"Can I delete photos that are stored on the cloud to free up space?"

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Ridding Items by Type from iCloud Storage:

Downloading All of iCloud:

Download all of iCloud. Then, search for your photos through use of Finder on the window. Cut & Paste them to another storage location. Then, trash what is in iCloud. Finally, upload what remains. Perform my User Tip: Getting a Quick and Direct "iCloud Drive-to-External Hard Drive" Download - User Tip