iCloud photos
Can I store selected photos in iCloud?
If you had set up iCloud photo library see this article https://support.apple.com/en-in/HT204264
And keep the box as checked for download originals in photo preferences see this article https://support.apple.com/en-in/guide/photos/pht5156cc968/4.0/mac/10.14
You must archive the photos see this article https://support.apple.com/en-in/HT204055#photos
And then delete the unwanted photos in www.icloud.com see this article https://help.apple.com/icloud/#/mm08b49040b5