I assume you are referring to a digital download. You should make a backup on an external hard disk drive / dropbox. If you did not keep a backup then you will need to call FMI so they can verify that you purchased FM and they should be able to send you a download link.
Thank you, Stacy. I tried to copy FileMaker in the few seconds at a time my laptop was working, but I got a message that the program could not be copied. I thought that I was OK anyway since I had done regular backups via Time machine/ Time Capsule. However, my backup folder (Time Capsule) was somehow "scrambled" when my new machine started backing up files, thus blocking/erasing the previous backup files in my folder on the time Capsule... So I'll get in touch with FMI.
Have a good day!