Im actually also helping a hospital currently replacing 6500 with 9300 cluster and I will also end up following same link Phoneboy sent you. For what its worth, way I do this is get show config text file and then copy sections over to new firewalls (we did this today).
K, dont laugh now, but I feel sort of obligated to say EXACTLY how this should be done, as I had people tell me before copying would always fail, so here it comes.
So on current firewalls, from expert mode, run -> clish -c "show configuration" > /var/log/hostname_date.txt
You can give it any name and send to any dir.
Then, once you get file off the fw, copy sectiions over till done (I would SKIP line for mgmt interface IP, since that would probably be different and default gateway line, until cutover time)
so hightlight portion you want to copy, then ctrl+c, then you console into new fw, right click and it will copy it over, do NOT do ctrl+v (believe it or not, then can mess up the process of copying right things)
Just to rest until whole config is copied, verify with show configuration and also web UI.
Also, maybe skip coping line set web ssl-port, as that can lock up console
Do NOT forget to run save config after every copy part.
Good luck and be free to message me if anything not clear.
Cheers mate.
Andy
Best,
Andy