Rio - I assume you are changing appliances, because on the same appliance it is possible to apply patch updates to take it from 8.1.2 to 8.3.1.
Backups have historically been patch-specific and I don't think I've heard anything from McAfee to suggest otherwise. I am surprised you are not seeing an error but because the last time I tried to restore a config from an older version it wouldn't let me. Knowing this I haven't even tried to restore an old config to a newer version for several years. I have always been told that it is necessary to install the correct version to the new appliance, restore the configuration and then upgrade it.
Thank you for your answer, i have backup file MFE firewall 8.1.2 and i try to restore it to my virtual appliance 8.3.1, but i didn't see any error, just notification that the admin console might disconnected because the firewall will restart automaticaly. i waited for an hour none restart happen on the firewall. I also tried on the appliance but had the same issue. When i log in to the firewall, the config are still default. What should i do next instead of input the config and rules manually???
As I mentioned, the only thing I know of is to build your 'target' machine with the same version as your source machine. Then restore the configuration and apply patches to take it to 8.3.1.
When we have customers replacing old appliances with new ones, this is what we have to do if the customer doesn't (or can't) upgrade the firewall software on the source apliance before taking the configuration backup.