I worked out where to put the code that you gave me and I changed the code to this:
<a href="[download_url]">[thumb_200x200]</a>
but when I click on the download url a zip file is opened that needs to be saved to the computer. The url has this at the end of the url
/?wpdmdl=139
How do I get this – /?wpdmdl=139 – not to appear at the end of the link