I've been looking for a Mac OS theme for Ubuntu for quite some time.
I came across MacBuntu, but I'd like to have something better. Then I discovered Mac for Linux: https://sourceforge.net/projects/mac4lin/?source=typ_redirect.
I downloaded it and extracted the files. It's written in the project's documentation - https://sourceforge.net/projects/mac4lin/files/OldFiles/Mac4Lin_Documentation.pdf/download - that I need to apply the GTK Metacity theme first - but I cannot find the proper window for changing a theme, despite having the Unity Tweak Tool. I cannot possibly start the process of changing the theme.
In 16.04, I put themes in Home > .themes
.themes is a hidden folder. You will have to use CTRL + H to view .themes and other hidden folders.
If you try CTRL + H and still do not find your .themes folder, you may need to create one.
Another location for themes is usr > share > themes
I somehow prefer .themes in Home folder for my custom themes though.
Get your Mac looking theme from the link below (it has many options )
https://www.gnome-look.org/p/1167049/