iPhone cannot be used because it requires a newer version of iTunes

I'm running Windows Vista Ultimate. This morning I updated my iTunes for Windows to 12.3.6 and I backed up my iPhone6. I just traded in the old phone and replaced it with an iPhone7. Now when I try to connect it to iTunes it says "the iPhone cannot be used because it requires a newer version of iTunes". I'm running the latest version. Any ideas?

As an aside, if this can't be worked out, is there a way to move the backup on my computer to iCloud so I can get it back on my phone?