This may not be possible.
If you own a 2013 ot 2014 iPad Mini 2 or 3 model, those iPad models cannot be upgraded beyond any version of iOS 12.
Currently, iOS 12 is at 12.4.9.
If your iPad Mini is an older iPad Mini and is currently running iOS 12.4.9, it is at is maximum OS version, currently.
Your iPad Mini maybe too old now.
Sorry.
If you need/want an iPad that can upgrade to thr latest iPadOS versions with access to current, updated apps, then you really need to seriously consider a new iPad model OR a “newer” , used iPad model capable of running the latest iPadOS versions.
There are plenty of newer, older iPad models that can run the current versions of iPadOS 14.
Sorry & Best of Luck to You!