I've read the open source parse docs, and looked at the parse c# sdk. I also looked at back4app but their example is way out of date. I can't tell if I'm supposed to take the c# code from the official parse sdk and try to put it in Unity or am I supposed to build a dll first? There's not a lot of information that I can find.
The latest official release for this SDK was in 2016, as you can see here: https://github.com/parse-community/Parse-SDK-dotNET/releases/tag/1.7.0
There's a fork of Parse SDK that usually works fine, have you already seen it? Here it is: https://github.com/fayezsalka/Parse-for-Unity-2018