Update support for iPad4 ended September 2017. The final iOS releases for this model were iOS 10.3.3 (WiFi Only models) and iOS 10.3.4 (WiFi & Cellular). iPad4 cannot be updated to any later major version of iOS as it lacks the minimum hardware requirements needed to run more recent versions. Your iPad4 uses a long ago obsolete 32-bit system architecture, while newer devices and Apps all use a 64-bit architecture.
You need to consider that compatible Apps for your iPad are no longer available. App Developers have dropped all support for 32-bit devices; 32-bit Apps have been retired and removed from the Apple App Store - which may severely limit the usefulness and utility of your iPad.
As such, if you want or need to access or use currently available Apps, requiring a more recent versions of iOS than your iPad is capable, you have no alternative other than to replace your iPad with a much newer or current model.
For information, here is a list of the highest version of iOS supported by the older models of iPad (for simplicity - “generations” are shortened to a number) that are restricted in their ability to be updated:
32-bit devices (obsolete)
iPad1 - iOS 5.1.1
iPad2, iPad3 and iPad mini1 - iOS 9.3.5 (WiFi Only models), iOS 9.3.6 (WiFi+Cellular)
iPad4 - iOS 10.3.3 (WiFi Only), iOS 10.3.4 (WiFi+Cellular)
64-bit devices
iPad Air1*, iPad mini2* and iPad mini3* - iOS 12.5.7
iPad Air2*, iPad mini4 - iPadOS 15.8.5
iPad5*, iPad Pro (9.7"/12.9" 1st generation)* - iPadOS 16.7.12
iPad6, iPad Pro (10.5"/12.9" 2nd generation) - iPadOS 17.7.10
iPad7 - iPadOS 18.7.2
(*) obsolete
Newer models are all able to be updated to the current version - iPadOS 26.1:
- iPad Pro 13" (M4/M5)
- iPad Pro 12.9" (3rd generation and later)
- iPad Pro 11" (1st generation and later + M4/M5)
- iPad Air (3rd generation and later + M2/M3)
- iPad (8th generation and later + A16)
- iPad mini (5th generation and later + A17 Pro)