How to remove right sidebar ad column?

[e9coupe]

I don't use ads on my site and would like to display the Latest Listings in four columns instead of three.  How do I remove the right side column for ads and display four columns?  I've tried everything I can think of but it's beyond my capabilities...

It won't let me upload a markup but you can see the site here.... https://bmwe3registry.com/list/   I'd like to add another column of entries to the right.