Hello ruthann333,
If you are using an iPhone 6s with iOS 11, then the photos taken may have been done on a newer iPhone model or with newer software. If the photo was edited, for example, you may be unable to share it. Do you see them on the iCloud website? Is that what you meant by you can see them in iCloud? Do they show up in the Photos app when you attempt to save them?
As an alternative, you could try having your friends share these photos through another method, like email: Share photos and videos on iPhone Then you can forward that email on.
However, these steps require you to be running iOS 12.5.7 or later. Which means, you'd need to update to this latest supported iOS version to complete those steps: Update your iPhone or iPad
If you still can't share the photos or wish to run a more recent iOS version, then it may be time to consider upgrading the device.
Hoping this helps out.
Take care.