how do i get ios 12 on my ipad mini 2? Been trying everything.. so frustrating

If your sure it is a Mini 2nd generation (see also these instructions:--> Identify your iPad model - Apple Support), you can update it to iOS 12.5.5 using a computer.

Learn how to update your device manually if you're using a Mac with macOS Catalina or later, or if you're using a Mac with macOS Mojave or earlier or a Windows PC.

Regards

Giulio

Sorry no.

An iPad Mini 2nd generation cannot support iOS versions beyond 12.5.5

An iPad 2nd generation cannot support iOS versions beyond 9.3.5-6

Why? because of hardware (CPU/RAM) incompatibility.

Perhaps your iPad is not a Mini model.

Regards

Giulio