I used Unity 8 years ago and most of this stuff was installed by default but now there aren’t even character controllers installed. I finally figured out you had to download them from the store but they still refused to load until I restarted Unity then they’d load normally for some bizarre reason. I’m trying to follow some tutorials but I hit a brick wall with “Environment”. The guy doing the tutorial just clicks on load environment and Unity happily does it but when I do the same thing I get a beep because it’s not installed. I went to the store but no luck so I even tried web searches but no luck. It’s a massive headache not installing standard content by default then not everything is in the same place you so you end up digging trying to find the missing parts. The environment pack I need includes things like water. Help!
Welcome back to the future - past Grayhand.
Did you say you used Unity 8, years ago. Or you used Unity, 8 years ago?
Is Grayhand your handle in the future also? 
Did you look here? You may want to start out with the Unity official tutorials first as they usually reference components properly and give direction on where to find them, if not included in the engine.