I purchased Lightroom 3 and have it downloaded on an old computer. It still works well. I got a new laptop. Is there any way to download Lightroom 3 (or any version after that where a Lightroom 3 serial number will work) so I can continue to use it?
You will need your Serial Registration Number for v3
You cannot buy, or use your serial number, on any later versions.
v3 is 'old' software. Good luck to get it running.
Your shiny new laptop deserves new software, and that would be a subscription to the Photography Plan (20GB) that gives you Version 10.4 of your Lightroom (Now called Lightroom-CLASSIC) along with the full version of Photoshop, Lightroom (Cloud Version), Lightroom on all Mobile devices, a Portfolio web site, etc.