need help updating ipad Model A1474 verson 8.2. when plugged in to computer ipad only ding over and over.

Also make sure you have updated iTunes on your computer to the very latest version. Your iPad has not been updated in years. In order to go the latest version, iOS 12.2 (you can't go any lower) you need the most current iTunes version.

Try a different USB port on the computer.

Continuous dinging usually points to a physical connection problem.

You try with genuine Apple USB cable?