How much do it cost for the new IOS update

The new IOS update doesn't cost anything.

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 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      

Use the links I posted above to do the update. Try Settings/General/Software Update to update.