Somebody at the selling company is going to have to do a License Transfer https://forums.adobe.com/thread/1355892
While you try and get the selling company to transfer the license to you, you should make a full backup of your hard drive to a USB hard drive so at the very least you have a recovery... I have NO idea what Mac software will do that, since I use a product that runs off of a Linux boot disc to copy everything on my Windows boot drive to backup
You might check the company to see if their program works with a Mac
The product I use is at http://www.terabyteunlimited.com/image-for-linux.htm
.
Image runs off of a bootable CD via Linux (the Zip you download includes a program to make the bootable CD) and it reads EVERYTHING on the drive, even the hidden registration information, so everything is restored when needed... and you may restore the image to a brand new drive in case of a crash, and not have to re-install anything