how do I get rid of the iCloud storage on my Iphone

You can't. iCloud is syncing storage. Anything in iCloud is also on all your devices signed into your Apple ID. You would have to disabled the syncing feature for each service, delete the items on the phone, and not turn it on again or else everything would appear again.

Change your iCloud feature settings [iOS and Mac] - https://support.apple.com/HT207689 - "'When you turn off an iCloud feature on a device, information stored only in iCloud for that feature is no longer available on the device. If you turn off Mail, Contacts, Calendars, Notes, Reminders, or iCloud Photos on just one device, you can still view and change your information on iCloud.com and on another device you set up for that feature."

My iCloud storage is full because of thousands of past emails .. how do I clear this old emails out of my storage? I don’t want to buy more storage I just need to get rid of these unwanted emails

Is this your iCloud email account? If so, you need to delete the emails.