Okay, something isn't adding up here, so let me try this again.
I downloaded version 1.3.9.h by following the link at zen-cart-com/index.php. On a test area, separate from the live site (which I think is 1.3.8.a but may be 1.3.7x) that the site owner accidentally destroyed by deleting the database (no, no backup available), I installed 1.3.9.h successfully. I then logged into the Admin module, and using the Tools | Template item (or whatever that's called), I selected from the list of available templates "Theme125" and applied it. It worked beautifully. I did not install any separate themes first, and did not download anything other than the installation file for Zen Cart.
Question 1) I have no idea what Template Monster is or why they are apparently evil or why everyone on this site apparently has taken a vow to never speak of them, BUT given all that it seems extremely unlikely that Zen Cart would be distributed WITH ONE OF THEIR THEMES INCLUDED! So, does Zen Cart ship with certain themes included (besides the default), and is it possible "Theme125" is one of them (as it seems to be)?
Question 2) If no themes (or at least, not the one I am referring to) ship with Zen Cart, how is it Theme125 is available to me immediately after installation (i.e., no other add-ons installed, etc.) - just by logging into the Admin module?
Now you may be wondering what's the problem then, you have installed Zen Cart and selected the theme you wanted -- get on with it. However, due to limitations of the web hosting company, using 1.3.9.h is not an option (even though I can and did install it manually, they only offer/support version 1.3.8.a). Yes, I know, I know - not secure, very old, evil, yada yada yada -- I get it, I do and I'm dealing with that down the road - first step is get the site live again. The problem is, a fresh install of 1.3.8.a from the web host did NOT include the Theme125 as described above. So:
Question 3) Assuming we are not talking about a Template Monster (or otherwise non-recommended) theme, is it possible to copy all the files that comprise a theme to a certain area of an ALREADY INSTALLED ZEN CART and then go into it's Admin module import the theme or have it automatically recognize the theme? If so, I could then copy the necessary files from the 1.3.9.h install to the fresh 1.3.8.a install and at least get the layout and look/feel reasonably close...