I did a normal install of Unity 2018.2.4f1, and notice at this point in the tutorial that there are no packages available to import on my Unity software - it only lists the Custom Package option. I reinstalled Unity in case I missed this as a selection option, but did not see it appear during the 2nd install. Is this particular tutorial package available in the Asset Store?
Unity is rebuilding the standard assets:
https://blogs.unity3d.com/2018/07/10/2018-2-is-now-available/
Standard Assets replacement
We have removed the 5.0 version of standard assets from the Installer in 2018.2 and are working on replacement packages for each part of the former prototyping pack. The first package (Standard Assets: Characters) will be available as a Preview soon after the 2018.2 release. It will contain a First-Person and Third-Person Controller integrated with Cinemachine, as well as a prototyping environment built with Probuilder. For details, watch for a blog post on the subject in the coming weeks. For those of you who need the legacy 5.0 package, it will remain on the Asset store.
For a link to some of the standard assets (they have variations) you can find it here: https://assetstore.unity.com/packages/essentials/asset-packs/standard-assets-32351