Download Lightroom 5.7.1

I have a paid version of Lightroom 5 but since original purchase I have changed my name and email address and computer twicw, so I am not recognised by Adobe even though I still have the original 24 number code and the order number. I now wish to install this on a new laptop and my original download is missing. I have tried a third party download but I only get 500 of my 5,000 photos. What can I do please?