Error building player because scripts have compile errors in the editor

So four years ago I took a Unity class in school and made a small game with Unity version “5.5. 1f1”. After I upgraded my MacBook to Catalina, the previous game app is no longer supported. I wanted to export the game again to play, but since I couldn’t open the older version of Unity, I had to convert the game project into version “2019.4.3f1” and tried to build the game from there. And when I tried to build&run the game, I got these error messages.

I looked it up on the thread and it seems like I need to move some scripts from one folder to another. But the problem is that I don’t know what I should be moving since I don’t find any scripts with the name they suggested, and double clicking the red icon doesn’t bring me to the script with compile errors.
If any of you knows what I should do, please let me know. The thing is, I already forgot almost everything about Unity and I didn’t have any coding experiences after that particular class. So please treat me like an idiot. Thanks.

Packing your project and use it in the Unity version you want to use