[LInux Mint] Can't find Cinnamon.css

I am trying to install a custom splash screen just a static jpg (apple logo on a black screen), and also change the font and opacity of the panel.
However, whenever go into .themes there isn’t anything in there. Although clearly I have a theme installed, called mac osx.
As shown here :

As you can see I have all the hidden files in view mode. I am a new user , anything simple I am missing?
18.1 ver. I don’t know any other relevant info about the build
Thank you
edit: bb code was a fail