You can’t.
You can only update to the current version, or the last version available to your iPad model; whichever is higher. iOS 11.x supports the iPad Mini 2, so that is your only update choice. Once Apple stops siging an older iOS version for your model, it is almost impossible to load that version. I only say almost because I’m sure some super hacker somewhere can get around the limitation, after much work.
What I recommend is that you consider the feature(s) you currenlty want/need jailbreaking for, then look over the current iOS version to see if they are still missing. Most of the features that people were jailbreaking for have been added over the last few years, or have reasonable alternatives. If you let us know what you want/need, someone should have an idea of whether it is possible in iOS 11.
Note: Older iOS version are usually only available for a few weeks after the newer version is released.