Im with phoneboy on this one. Here is what I would suggest...so on R77.30 device, from expert mode, just type clish -c "save configuration" > /var/log/config_backup.txt
That will generate file called config_backup.txt in /var/log dir, which can be used on the new device from clish to run load configuration /var/log/config_backup.txt )or whatever dir you copy the file to).
Now, here is tricky part...for this to work, config file has to "match" new device, meaning interface names would need to match and whatever else is in the original config file and easiest way you would know this is when you run load configuration command, it would error out at whatever line cant be copied over and then you need to go back and modify that line to continue when running command next time.
It might be tidious work, but most likely your best bet.