How to change number of columns in main footer area?

POFO has options to change number of columns in main footer area globally as well as you can set it page / post / portfolio level.

Change number of columns in main footer area globally for whole website

Please refer this article: Theme Customizer > Footer > Footer

Change number of columns in main footer area page / post / portfolio wise

Please follow below mentioned steps.
Step 1: Go to WordPress Admin > Add/Edit page/post/portfolio
Step 2: Find POFO page/post/portfolio settings > footer main
Step 3: You can changing columns sidebar to on / off to change number of columns display in footer. Please check below image for more information.