Thank You as a Popup

Hello, I've looked through different threads here, to do with my question, but all are incomplete...broken links, referencing things that are no longer available.  Is this possible?  If so, can you please point me in the right direction?  

va.northwaydesigns.com, simple little email collector in the footer.

This is a Wordpress site and I'd love to keep it as simple as using Popup Maker plugin, which calls a class.  Any way to add this class? 

You can redirect your "Thank you" page to a custom URL which contained the pop-up page.

https://www.jotform.com/help/211-Setting-up-the-Thank-You-Page

But if you want to pop up your Thank You without redirecting to another URL, you may need to download your form's SOURCE CODE and add a custom script to display your Pop Up window.