How can I get a software update

IOS software update?

According to the screen shot, you don't have a WiFi connection, You have to have a WiFi connection to update.

See the articles below.

Update your iOS device.        

Get help with over-the-air iOS updates          

Update – Can’t or can’t restore 

Have you tried using iTunes on a computer or Finder if running Catalina or later to do the update?

 Update software on iOS devices in iTunes on Mac

If you see an error when you update or restore your iPhone, iPad, or iPod      

Updating iOS: common issues and solutions

Follow these steps to upgrade to the latest version of iOS, depending on your device this should be iOS 14.6

You are currently using Mobile Data / LTE. You need a Wi-Fi connection (or a connection to a computer with WiFi via iTunes)

If you don't have WiFi at home, ask a friend or you can go to an Apple Store.