Your very old first generation iPad mini can be updated to iOS 9.3.5 (WiFi Only models) or iOS 9.3.6 (WiFi & Cellular models). It cannot be updated to iOS10 or any later major version as its internal hardware does not meet the minimum technical requirements for update to newer versions. Apple ended update support for the original iPad mini in September 2016.
Apps that remain compatible with older iPad models, such as yours, are increasingly difficult to find. Third-party developers are systematically dropping App support for older versions of iOS preceding iOS11/12. Withdrawal of support for older versions of iOS is making the utility and usefulness of older iPad models increasingly limited.
As older versions of Apps are removed from the Apple App Store, you’ll not be able to (re)download or (re)install them. It is for this reason that having deleted on older App you are now unable to re-install it.
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.
Sorry - I’m sure this isn’t the news that you were hoping to hear. The good news, however, is that any purchased Kindle Book titles are still available to you from your Kindle account. These can be downloaded again to any of the current Kindle readers or Apps.
I hope this is helpful to you, of only in explaining what has happened - and in outlining your options.
