Need to update

You can update as described in Update your iPhone, iPad, or iPod touch - Apple Support

Note that one of the methods is via iTunes and that can be done using a Windows computer.

Also note that if you have the original iPad Mini it cannot be updated beyond iOS 9.3.5 no matter what method you try.

Windows computers can run iTunes just like a Mac can run iTunes.

Is your signature correct in that you have an iPad with iOS 9 on it? If you have the original iPad Mini, you cannot update it beyond iOS 9.3.5 if that's what you're hoping to do.

If your iPad Mini has been stuck all of these past years on iOS 9.3.5, then you own a 1st gen iPad Mini.

A 1st gen iPad Mini cannot be upgraded/updated beyond iOS 9.3.5.

It is a nearly 6-year old mobile device.

Its internal hardware is too old, underpowered and completely incompatible with any of the later, present and future versions of iOS.

Sorry and Best of Luck to You!