To be more specific,here is what they say on the Google site and where I am not understanding them (in red):
III. Conversion tracking & Hypertext Preprocessor (PHP)
Follow these instructions to insert the conversion tracking code to a website created using dynamically-generated PHP: Hypertext Preprocessor (PHP) pages.
To add conversion tracking code to PHP pages using your web page editor, complete the following tasks:
1. Open your conversion confirmation page PHP file. If multiple pages are generated from the same file, find the section in the PHP file which generates your conversion page.
Where is the conversion confirmation page?

2. If your site has a variable conversion value, determine the PHP expression that displays that value. For example: <?php echo $totalValue ?>, <? echo totalValue ?>
Choose the [FONT=Courier New]Purchase/Sale [/FONT]conversion type while going through the conversion tracking setup. Insert the full string (<? echo $totalValue ?>) into the "Revenue for your action" field and click Save Changes & Get Code to generate the final tracking code. Click 'OK' when you're prompted about using an unrecognized value. Copy and save the resulting code snippet .
I don't think that Zen Cart has a variable conversion value, does it?

3. Insert the conversion tracking code onto the conversion confirmation page. Make sure that the code appears within a static HTML section, not contained within an PHP code section (delineated by <? and ?> markers).
Insert the conversion tracking code snippet directly into the body of the conversion confirmation page. Search for the </body> tag and place the code immediately above it.
If the </body> tag is not located within the static portion of the HTML page, make sure that you add the code snippet so that it appears within the <body> section of the page.
This seems pretty straightforward. It's just the where of the final conversion page that I think is hanging me up.