This is correct.
A 2013 iPad Mini 2 or 2014 iPad Mini 3 cannot upgrade/update beyond ANY version of iOS 12, currently at iOS 12.5.
The internal hardware in these iPad models is too old and too underpowred to handle snd run all of the new, advanced and hardware resource intensive features of iPadOS.
Sorry.
If you need/want an iPad with an up to date iPadOS with access to current, updated apps, then you really need to seriously consider a new iPad model OR a much “newer” , used iPad model capable of running the latest iPadOS versions.
There are plenty of newer, older iPad models that can run the latest, current versions of iPadOS.
Sorry & Best of Luck to You!