iCloud backup
When backing up photos on iCloud, it is coming up with the messages that photos will be deleted from finder. Does this mean they will be deleted from my phone?
Question marked as
Yes. If you have photos on your phone that were placed there by syncing them from a computer (via iTunes or Finder), if you turn on iCloud Photos on that phone, they will be deleted. The originals would normally be on the computer that you originally synced them from, so one option would be to turn on iCloud Photos on your phone and allow the photos to be deleted from the phone and then manually upload those photos from the computer to the Photos app at iCloud.com. Other options are discussed in the "What if some of my photos and videos are missing after I turn on iCloud Photos?" section of Get help with iCloud Photos - Apple Support
Also note that iCloud Photos is a syncing service (not the same in all respects as backups and not the same as iCloud Backup).
iCloud Photos is a syncing service. Any photo you delete from a device where iCloud Photos is turned on will also be deleted from iCloud and from any other device connected to iCloud Photos. You can potentially reduce the storage space required on a device by turning on Optimize Storage. See: Set up and use iCloud Photos - Apple Support
Apple does not currently offer cloud-only storage for photos. If that is what you want or need, you may want to explore 3rd party options such as Google Photos or Dropbox.
Another way that photos may be on iCloud (if you don’t have iCloud Photos turned on) is via a backup of an iOS device. The only thing you can do with a backup is use it to restore a device or set up a new device. The contents of backups are not viewable at iCloud.com and if you delete a photo from a device it will not be included in future backups and will be lost.