I have old ipad with iOS 9.3.6 version,when I am trying update it say your software is up to date.

You clearly have an iPad2, iPad3 or original iPad mini. These devices cannot be updated beyond iOS 9.3.5 (WiFi Only models) or iOS 9.3.6 (WiFi & Cellular).

Apple ended update support for these devices in September 2016. None of these models can be updated to iOS 10 or later versions, as the internal hardware does not meet the minimum technical requirements for new versions of iOS/iPadOS. The 32-bit architecture upon which they are based is effectively obsolete.

Most App Developers have also dropped support for older devices and iOS versions preceding iOS10 - and have withdrawn older versions of their Apps from the Apple App Store.

If Apps that you need to use now have higher minimum iOS-version requirements, your only option is to replace your iPad with newer model. Of current models, even the iPad8 supports current iPadOS 14 - and has hardware specifications and capabilities will vastly outperform your old iPad

I hope this information and clarification is helpful - if only in clearly stating the limitations of your current iPad and you potential options.

Given information already provided, you having an iPad4 is very unlikely.

You’ll find your model number here:

Settings > General > About

Not sure which iPad you have? Identify your iPad model.

An iPad running 9.3.6 isn't capable of 10 or above.

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