How do I transfer iPhone storage to iCloud storage?

You have plenty of space on your iPhone (only 50GB used). iCloud does not add space, nor can you offload from your phone to iCloud. You can elect to optimize storage in photos (settings > photos) to reduce the size of photo storage on your device. Originals will be kept in icloud with optimized versions on device.

I don't see any problem with your iPhone storage and it does not appear to be anywhere near full. What makes you think your iPhone storage is full?