First, the upgrade method is more troublesome, and not likely to succeed.
Second, the recommended new 8.0.x server, and database into the new server.
Method has been successfully used as follows:
1, the installation Navicat 12.0 or later connected to the old version 5.x database, and backup; (backup format in this case is: nb3)
2, connected to the high version of the server, and set up the empty database and restore from the specified file (file backup of the previous step), you can.