Well, you should save your downloaded installer, burn it on a CD, upload to drop box or put it on a Flash drive so that you can re-install when the need arises.
Without that, you'll have to contact customer service, provide proof of purchase and ask them to send you a new download link for the installer.
I actually did save the downloaded file but when I tried to install it I got a message that says it's is an unidentified developer.. I am sending a screen shot.
Hold down the control key when you launch the FMP installation package for the first time…or temporarily change your System Preferences>Security & Privacy>General to allow apps downloaded from "Anywhere".
Many thanks, it worked!