The first generation iPad Air, iPad mini2 and mini3 can only be updated to iOS 12.5.7.
Apple ended major update support for these models of iPad in September 2019 - although they have since received occasional “point” security updates, the most recent being released January 2023. These devices cannot be updated to iPadOS 13 (or any later major versions of iPadOS) as the internal hardware does not meet the minimum technical requirements (CPU capabilities and available RAM) for newer versions of iOS/iPadOS.
Whilst some App titles remain compatible with your iPad, if you want or need to access to Apps requiring more recent versions of iOS, you’ll need to consider replacement of the iPad with a newer or current model that supports iPadOS16/17.
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 15.8.2
iPad5, iPad Pro (9.7"/12.9" first generation) - iPadOS 16.7.7
(*) obsolete
Newer models are all able to be updated to the current version - iPadOS 17.4.1
- iPad Pro 12.9" (2nd generation and later)
- iPad Pro 11" (1st generation and later)
- iPad Pro 10.5"
- iPad Air (3rd generation and later)
- iPad (6th generation and later)
- iPad mini (5th generation and later)
In conclusion, it would perhaps be unwise to consider purchase of any iPad that does not appear within the list of devices capable of running iPadOS 17.x.
As for the device that you have, it may be too old to have any residual value for trade-in with Apple. You might alternatively consider selling privately - but be mindful that the potential buyers will find the device as restrictive for use as you yourself have discovered.
You can establish both eligibility and potential value (if any) for Apple's trade-in program in your country/region here:
Apple Trade In - Apple