How to download iPad Mini simulator

I don't know about the earlier releases but you can do this on Xcode 10.2.1(or later)

Select Add Additional Simulators... from the active scheme:

Then press + to create new Simulator and select iPad mini in Device Type:

By popular demand, Xcode now includes the iPad mini Simulator. It is not created by default, but you can use the Xcode Devices & Simulators window or xcrun simctl from the command line to create one.

For example, to create an iPad mini 4 simulator with Xcode 11.2:

xcrun simctl create "iPad mini 4" com.apple.CoreSimulator.SimDeviceType.iPad-mini-4 com.apple.CoreSimulator.SimRuntime.iOS-13-2