ok, that output tells me that the tape drive is already configured and can be used (rmt/0) and your second hdd has c0t1d0 as target device id.
you said that data is on it, do you know on which slice/partition?
e.g.: if you want to mount slice 0 of the new disk on /mnt you could use:
# mount -F ufs /dev/dsk/c0t1d0s0 /mnt
gP
btw: how old is that machine with 4,5 GByte disks?