Failed to load 'Assets/Plugins/VuforiaWrapper.dll', expected 64 bit architecture ?

I install unity version 5.3.1f1 and import Vuforia SDK from
https://developer.vuforia.com/downloads/sdk
when I run and build from unity i have this problem ?

You’ll need the 32-bit version of Unity to make the plugin work. While 32-bit application can run on 64-bit systems, you can’t load 32-bit DLL’s from 64-bit applications and vice-versa. Vuforia is (obviously) a native plugin and it would seem as though only a 32-bit DLL is included. As to why they don’t provide 64-bit DLL’s, I have no idea. +1 to ARToolkit for supporting all platforms.