What platform are you using? Apple OS or PC Win x x?
On a windows system the VST’s are usually installed into System/c:/program files/Vstplugins (64bit) pr (32bit) usually System/c:/Program Files(x86)
Inside cubase, look under the Devices drop down menu (top task bar) and go to the Plug in manager, open that up and you’ll be able to add path settings for other drives/folders that you may have installed plugins into.
The media bay won’t re organise third party instruments or presets unless they’ve been opened and saved back as a preset in the Cubase format.
When you’ve set the relevant paths in the plug in manager, you can then point the plug in (once its’s launched to it’s specific library, ie kontakt libraries on a different drive.