Software upgrades

Your very old iPad2 can, theoretically, be updated to iOS 9.3.5 (WiFi Only models) or iOS 9.3.6 (WiFi & Cellular models). iPad2 cannot be updated to any later major version of iOS as it lacks the minimum hardware requirements needed to run more recent versions.

You may wish to consider that compatible Apps for your iPad are increasingly difficult to find - as third-party developers are increasingly dropping support for older versions of iOS preceding iOS11/12 (and some, for technical reasons, have dropped support for all iOS versions preceding iPadOS13). As older versions of Apps are removed from the Apple App Store, you’ll not be able to (re)download or install them. As such, if you want or need to access most current Apps, you’ll need to consider replacement of your iPad with a newer or current model.

Even the most basic current iPad7 will massively outperform you current iPad - and is compatible with the vast majority of current Apps

You can't it's too old. Min requirements for iOS 13:

https://support.apple.com/en-gb/HT210327

You don't. Your iPad is simply too old and too under powered to run the now required 64 bit software. If you want and need the newer iOS versions, you will have to buy a newer iPad.