Hi,
Honestly, I don't know how Google Adwords work. That plugin was provided by a third party developer as he needed it for Google Adwords.
We checked that the snippet of the plugin is added properly to the products page and that the code is correct in the plugin.
But we never tested it ourselves.
I realize that what I said previously here is wrong. This plugin is adding the conversion snippet to the product pages, not at the end of the checkout. So it's probably not what you want to do. Instead, you want to edit the file "end" of the checkout view via the menu Display>Views and add your snippet of code there so that it displays at the end of the checkout.
Again, I don't know how to test as I don't know Adwords. I guess that you should get something displayed in your Adwords account when someone goes through an Adwords link and purchase something.