How to update to i0s

I see you marked your post as Best Answer. People normally mark a post as Best Answer when it answers the question and no other replies are needed. If you mark a post as Best Answer when you are still looking for an answer, it may slow down any responses to your question. 

But I’m guessing you would still like to find out how to update the iOS on your iPad Mini 4. First, please understand that the highest your iPad can be updated is 15.7.9.

To update your iPad, select Settings > General > Software Update. If your iPad is eligible for an update, you will be prompted to do so. You can find more details here:

Update your iPhone or iPad - Apple Support