Why can't I access Unity Pro Standard Assets on my new install?

Hello, i am a beginner. i installed free version of unity3d, then launched it, opened new project, and could not find pro-standard assets. there are only standard assets. what could be the reason ? how to solve this problem ? thanks.

In order to use pro assets, you need to have a pro license or start your 30 day pro trial. Once you have used up your 30 day trial you can not install Unity Pro Trial on your machine again.

The pro standard assets should be in the same list as the standard assets when creating a new project, generally ending in (Pro only). If you want to add them into a project you've already created, go to the place you installed the editor and look for the Standard Assets folder, they'll be mixed in with the normal standard assets in there

Just remember that some shaders and scripts only works in Pro version.