NOTE: this is a high-level description of a process that leaves out quite a few substeps. If it seems mysterious or just makes no sense to you, then consider engaging RSA Professional Services to assist you with the migration.
You should be able to downgrade one of the new hardware appliances to 8.1 (requires installing the 8.1 hardware appliance iso and patching to match your existing Primary) and then restore your backup there. Do whatever cleanup you need (remove the old replicas from the restored Primary, etc.). Upgrade that one to 8.3, THEN attach the remaining new appliances as Replicas, then you can distribute the new sdconf.rec.
Hi,
you can only do a restore on the EXACT Software Version you run the Backup.
So you need to upgrade your Production from 8.1 to 8.1.1 to 8.2 to 8.2.1 and finaly to 8.3.
There is no shortest way.