Broken Download Link for Lightroom 3.6

If you purchase it from Adobe or previously registered the product, then the installer could be in your online account. See the instructions on Adobe's help page and see if that works:

How to download your older app

If not, then try this – but make sure to follow the download instructions first:

Adobe Lightroom 3 Direct Download Links

Hope that helps.

That is a really old version, so Adobe may have removed the installer

I do not know how far back this process will go, but try this link
-NOTE that you will have to search the site for your specific download
Direct Download Links https://prodesigntools.com/tag/ddl MAY help
-you MUST do what it says in Note: Very Important Instructions
-https://prodesigntools.com/adobe-cc-2015-direct-download-links.html#download-instructions
-the prodesign links go directly to Adobe's file server, so this process will
--only work until Adobe completely removes the old version(s) from the server
.
IF/When you do have a download, be sure to copy it to AT LEAST one external device
-since Adobe does sometimes remove old versions from the server
-a usb flash drive or external hard drive, or write to a DVD
-plus a text file containing your serial number if you have a serial number program