Mounting a partition from freebsd 6.2?

[mojo fms]

I was working on an upgrade to 6.3 from 6.2 and I lost power during the
install which hosed most of my system.  Instead of trying to really recover
it I decided to just rebuild.  I have a backup of my /etc and /usr/local/etc
on a different drive that should be fine, it was just mounted under /mnt
normally and used for backups.  My problem is that I installed 7.1 and was
careful not to erase any data on that drive, but my only options for a
partition to mount is /dev/ad2s1.  When  I try to mount that it gives me
"mount: /dev/ad2s1 : Operation not permitted", what can I do to get the data
off of it?  I only really care about my /etc information  but it would be
nice to get all of the information off of it.