There's no need for you to format anything. There's really no need to even remove the partition tables at this point (though that will probably be necessary before you can actually add the drives to a pool). The problem is that FreeBSD isn't seeing the drives at all, which is likely due to either outright hardware incompatibility or improper BIOS settings. A Linux distro will help narrow down the issue. It isn't dispositive, as the HCLs are quite different between Linux and FreeBSD, but it will at least give a data point.