How do I identify which theme a blogger is using?

I have created some wordpress pages which are accessed through links in the footer. These pages are for FTC required disclosures, such as Privacy Policy, TOS, Earning Disclosures, etc. They are created from "blank" pages which have had static content.inserted where I think what you call "the loop" would ordinarily be.

So far, the only WP type features I have included are the header and footer as the sidebars seem to vary a bit in name and number according to the theme. I would like to included sidebars, so the pages fit the theme look even more, but I do not know how to identify the theme.

Where would I find instructions for identifying which theme is being used, and how to write an "if-then" type selection for loading the appropriate sidebar?

Does anyone have examples?

Thanks in advance.

addendum ... thought you might want to see the code for the blank page before I removed the inappropriate (for my current theme) sidebar and replaced the "Hello" with my text. Following the instructions from the site where I found this code, I placed the pages in my root WPMU directory so they can be used by all themes.

define('WP_USE_THEMES', false);