iPad mini 1st generation

If re-installing the Operating System, you will need to restore the iPad to factory settings. The process uses a Windows PC (with iTunes for Windows installed) or a Mac computer (with iTunes or Finder - as appropriate for the installed version of macOS) to download and install a fresh copy of the most recent supported version of iOS:

Restore your iPhone, iPad, or iPod to factory settings - Apple Support

You need to understand that all 32-bit models of iPad are long-ago obsolete. If you manage to successfully factory restore - installing a fresh copy of iOS - you will not find any Apps to install. All Developers has dropped all support for 32-bit devices; all 32-bit Apps have been withdrawn from the Apple App Store. As such, at best, the iPad will be almost useless.

Are you suggesting that your iPad mini1 doesn’t currently work? If it does, it can be updated to iOS 9.3.6 - and no further.

iOS 9.3.6 is the only version of iOS that can be installed. If this needs to be reinstalled, follow these instructions:

Restore your iPhone, iPad, or iPod to factory settings - Apple Support

All System Updates are digitally signed by Apple - and can only be installed whilst the digital signatures remain valid. After release of a new iOS/iPadOS version, the immediately preceding version continues to be digitally signed by Apple - however, usually within a few days, Apple will revoke the digital certificate with which the earlier version is signed. As such, you can only (re)install the most recent available release for any model of iPad.

Here is a list of the highest/most-recent versions of iOS supported by the older models of iPad (for simplicity - “generations” are shortened to a number), noting that older models 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 15.7.3

Newer models all support the current version, iPadOS 16.3.1

• iPad Pro (all models)
• iPad Air (3rd generation and later)
• iPad (5th generation and later)
• iPad mini (5th generation and later)

1st_generation_iPad_mini wrote:

No I mean an OS that will be compatible. I honestly don't have a clue how to go about it. I assume I type something on my browser. If you can help me I will be much obliged. Please assume you are dealing with a complete nit!

Go to (Settings > About) and find what it has for "Software Version". I'm guessing that you got it used, and I'd be surprised if it hasn't already been updated to the most recent version (probably 9.3.5). There is a 9.3.6 update, but that's only for cellular models. 9.3.5 is over 6 years old and 9.3.6 (only fixed issues with iPhones ad cellular iPads) is over 3 years old.

You can’t. You can only install the current version available for that device. That would be 9.3.6.

Do you mean original as in the absolute original? Apple doesn’t give any means to go back to an earlier version. But the latest compatible version should still be available on Apple’s servers.