Update 3.2 to 5.7.1 (like my old computer)?

Hello, I'm new to this community and I'm hoping someone can help me. I purchased Lightroom 3.2 over 10 years ago and had it on my old computer. During that time, apparently Adobe updated it to 5.3, then 5.6, and finally 5.7.1. I installed the original 3.2 on my new computer and I'd like to get it updated just as the old computer was. I fired up the old computer and found the installation files for 5.3, 5.6, and 5.7.1 that had been downloaded from Adobe but when I installed 5.7.1 it asks for a serial number. I used my 3.2 number but it didn't work. Does anybody know how I can get it to work, like it did on my old computer? I still have the old computer if I need to search for a particular file that needs to be copied to the new one. Thanks for any help you can give me. I know I'll eventually have to go the subscription route but I'd rather not just yet.