If you are using the '2016 R3' SDK then you will not find a Unity Toolkit because it does not have one, as its structure is very different from previous SDK versions, as explalined in my setup guide for Unity in R3.
If you are using the '2016 R2' SDK, then the Toolkit is in the C:/ > Program Files (x86) > Intel > RSSDK > Framework > Unity folder of your SDK installation. If you open a Unity project and then run the 'UnityToolkit' package file, a list of toolkit files will appear in Unity in a pop-up window. Click the 'Import' button on that pop-up window to add the Toolkit files to your Unity project.
The Unity samples, meanwhile, can be accessed by an application called the Sample Browser. This is in a folder called 'Intel RealSense SDK Gold' that is placed on your desktop when the SDK is installed. If you run these samples from the Sample Browser then they will automatically load into Unity so that you can then Run them using the 'play' triangle in the top-center of the Unity window.
If you need to remove R3 and install R2 instead, I recommend using this direct download link for R2 once R3 is uninstalled: