Hello kopaczBea,
Thanks for using the Apple Support Communities! I understand you are trying to separate two iCloud accounts and are worried about losing the photos. I'm happy to help you find some information.
First, I would suggest you sign in to your Apple ID on https://www.icloud.com/photos to see if the photos on your iPhone appear. If they do not, follow the steps under the "Photos and videos" section in the resource below to make a copy of your photos:
Archive or make copies of the information you store in iCloud
Once that is completed please follow the steps here:
What to do before you sell, give away, or trade in your iPhone, iPad, or iPod touch
If you have any issues after reviewing the links, please let me know.
Have a good day!