My iPhone 6s apps update doesn’t show on the App Store

I’m not sure if you’re asking about an app update, or an iOS update...

If it’s an app, try to update your iOS version to 14.4.2 (current), and try the app update again.

Settings > General > Software Update

If the above doesn't work, have you tried signing out of the App Store/iTunes, restarting the device, and then signing back in?