cannot update ipad A1403 to ios 13

That iPad model is too old to upgrade past its current IOS version.

That iPad model’s internal hardware is too old, underpowered and completely incompatible with any current and future

versions of iOS.

Sorry.

If you need an iPad that can run the latest and greatest versions of iOS, as well as, the most current apps available, then, you will need to purchase a new iPad from Apple or a discounted, refurbished iPad from Apple’s Refurbished & Clearance section of Apple’s Website.

Best of Luck to You!

In addition to the other comments, iOS 13 is not an available update for iPad, regardless of which iPad model you have. Apple is releasing iPadOS 13 specifically for iPads going forward. Regardless, it still will not be available for your iPad model as the others have already mentioned.

You have the 3rd gen iPad.

This iPad only supports iOS 9.3.5/9.3.6 and below that.