I thought I would reply here before I head off to the land of sleep (2am for me).
You can do a 3 column layout, but you will need to modify a theme file. This means setting up a child theme and then copying over a file from the parent theme into the child, then making the modification.
However, it won’t always be 3 columns as this is a responsive theme and as the screen gets smaller, it will go from 3 columns to 2, then to 1 on phones. By default, it’s set to be 4 columns, then responsive down to 3, then 2, then 1 as the screen goes smaller.
I can point you to the file that you would be editing if you still want to do this? Probably have to wait until I start my day tomorrow though.