It looks to me like you are looking in the macOS “global” library (
/Library). You also have a user Library (
~/Library) which is where the plugins are stored.
To get to your Library, navigate to Finder > Go > Go to Folder… and enter the following path:
Hope that helps,
PS: I should note that, by default, the user Library (
~/Library) is hidden in Finder…that’s why you don’t see it in your screenshot. You can find instructions for changing this at the bottom of this guide.