The previous version is 3.1.1. It was installed with the .tar.gz file (files located at /usr/local/wildfire).
I tried first to upgrade with the new dmg installer and the installer overwrited my old installation. The server was not working. I removed the directory to try an installation from scratch, but the installer failled to reinstall a second time.
I finally downloaded the tar.gz file and unpacked it and I copied my old conf and embedded-db directories… I still have the same problem with this installation.
So, I removed this version and I restored my backup from 3.1.1 for now.