why cant i download apps on my ipad

Start here:

If you can’t download or update apps on your iPhone or iPad – Apple Support

If you are experiencing difficulties with adding or removing Apps to/from your iPad, you need to check your ScreenTime restrictions:

• Settings > Screen Time > Content & Privacy Restrictions > iTunes & App Store Purchases > Adding Apps - ensure that this permission is set to Allow
• Settings > Screen Time > Content & Privacy Restrictions > iTunes & App Store Purchases > Deleting Apps - ensure that this permission is set to Allow

If your iPad is an older model, incapable of update to current versions of iOS/iPadOS, Apps may have version requirements that are greater than your installed version of iOS. The tags appended to your post suggest that you have an iPad mini1 with iOS9 installed.

iPad2, iPad3 and iPad mini1 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. Your 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 obsolete.

You may need to consider that compatible Apps for your iPad are increasingly difficult to find - as most developers have dropped support for 32-bit devices and iOS versions preceding iOS11/12/13. 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, you’ll need to consider replacement of your iPad with a newer or current model.

Of current models, even the entry-level iPad9 has specifications and capabilities that will massively outperform you current iPad - and is compatible with the vast majority of current Apps. Other models are more powerful still.

I hope this information provides clarity as to your available options - and the potential limitations of your iPad.

Perhaps, if it is still running iOS 9 (as per the product list at the bottom of your question) it cannot support more recent iOS versions because of hardware (CPU/RAM) incompatibility.

Obviously it can't even support apps that require iOS versions past 9.3.5/6.

Regards

Giulio