You do not have an iPad Mini 2.
You have an 1st generation iPad Mini 1.
If you had a Mini 2 you would've been getting message for upgrades/updates for iOS 10/11/12 right along.
An iPad Mini 1 cannot upgrade past iOS 9.3.5.
Its hardware is too old and underpowered.
I would STOP using that 2-2-1/2 year old Safari web browser, as it is, probably, not safe and secure to use any longer, and seek out a third party web browser that is STILL currently being updated and STILL being supported on iOS 9.3.5.
Here are a few third party web browsers that I know are STILL being updated and supported on iOS 9.
Popular third party, iOS 9 and earlier compatible Web browsers are more quickly dwindling, now.
Older iOS devices and users had about a dozen popular, well known and secure, third party Web browsers to choode from at one time.
We are down to six, now.
Here’s what’s left.
iCab Mobile Web browser
Dolphin Web browser
Snow Bunny Web browser
Private Browsing Web browser
Aloha Web browser
Maxthon Web browser
Good Luck to You!