Unfortunately, there's not much that you can do...
The iPad mini1 along with the iPad2 and iPad3 can only be updated to iOS 9.3.5 (WiFi Only models) or iOS 9.3.6 (WiFi & Cellular models).
Apple ended update support for these models in September 2016. These models of iPad cannot be updated to iOS 10 or later major versions of iOS, as the internal hardware does not meet the minimum technical requirements for new versions of iOS/iPadOS. This limitation cannot be bypassed; these are 32-bit architecture devices, whilst all recent versions of iOS/iPadOS are designed for 64-bit hardware platforms. iPad2, iPad3 and iPad mini1 are fully obsolete.
You need to consider that compatible Apps for older models of iPad are no longer available - as App Developers have dropped all support for 32-bit devices. As older versions of Apps are removed from the Apple App Store, you’ll not be able to (re)download or install them - which may severely limit the usefulness and utility of your iPad. As such, if you want or need to access most current Apps, requiring more recent versions of iOS than your iPad is capable, you’ll need to replace the iPad with a much newer or current model.
Also be aware that, for security, many commercial websites mandate that visitors use computers that are both using a current/supported version of the computer's host Operating System - and secure version of web browser software. The Safari browser built-in to iOS will be too out of date to be usable with many websites.
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 16.7.8
(*) obsolete
Newer models are all able to be updated to the current version - iPadOS 17.5.1
- iPad Pro 13" (M4)
- iPad Pro 12.9" (2nd generation and later)
- iPad Pro 11" (1st generation and later + M4)
- iPad Pro 10.5"
- iPad Air (3rd generation and later + M2)
- iPad (6th generation and later)
- iPad mini (5th generation and later)
