Make sure that you have the correct installer - https://developer.vuforia.com/resources/sdk/unity

When you execute the installer, it will ask you where you want to install the Vuforia Unity extension. You can use the default folder or select your own. The installer will place a unitypackage containing the Vuforia Unity plugin(s) and SDK libraries in this folder.

You can import the Unity extension to your project by either clicking on the unitpackage in its installation folder, or importing it to your Unity project from the menu using Assets > Import Package > Custom Package and selecting the extensions unitypackage from the installation folder.