ReadyNAS 102

Before you invest in anything, do you have the ability to test the drives with the vendor's tool?  If the volume is damaged, it's likely because the drives are damaged, not that the data just got corrupted.

If the drives pass vendor diagnostics, the issue could just be the power supply.  NAS with external supplies, like your 102, are fairly well isolated by the supply from events like that.  It's just a basic 12V 5A supply with a standard 5.5mm x 2.1mm connector.  Some of the cheap supplies can't provide good initial inrush power, so choosing a 6A or 7A can be good if you are using drives that require a lot of power to spin up, like enterprise models.  I recommend you look for one that expressly states that it's also for CCTV cameras or some device other than LED lighting.  LED lighting doesn't require the same level of regulation as most other complex electronic devices.

If the drives can't pass vendor diagnostics, then the surge did get into the NAS chassis, and it's unlikely anything will help.  But if at least one passes, then recovery may still be possible.

Unfortunately, though, the other thing on the NAS that is subject to damage by a lightning event is the network transceiver.  A power supply may get the NAS booting again and still leave you with no way to get to the data.  This is more likely if you have an Ethernet cable running from your house to the barn and no switch or Ethernet surge protector in the barn.