Welcome, WDBonline, to Apple Support Communities!
An iPhone 6 cannot be updated/upgraded past iOS 12.5.5.
However, I’m not sure that you are in need of an iOS update or upgrade.
On the other hand, iOS 12.5.anything is significantly out of date, and has difficulty even updating Apps, since few, if any, apps, available, these days, will run on that old an iOS.
If you have a computer (PC w/iTunes, or Mac with iTunes, or Catalina or newer using the Finder), you may be able to get the iCloud updated.
Otherwise, I would recommend contacting Apple at the link in the upper right: Get Support .