can't mount USB disk

I'm trying to mount a usb disk used as a backup device on a win7 system:

$ gpart list da0
Geom name: da0
modified: false
state: OK
fwheads: 255
fwsectors: 63
last: 2930277166
first: 63
entries: 4
scheme: MBR
Providers:
1. Name: da0s1
    Mediasize: 1500300329472 (1.4T)
    Sectorsize: 512
    Stripesize: 0
    Stripeoffset: 1048576
    Mode: r0w0e0
    efimedia: HD(1,MBR,0xfa273430,0x800,0xaea86f21)
    rawtype: 7
    length: 1500300329472
    offset: 1048576
    type: ntfs
    index: 1
    end: 2930276128
    start: 2048
Consumers:
1. Name: da0
    Mediasize: 1500301909504 (1.4T)
    Sectorsize: 512
    Mode: r0w0e0
$ gpart show -l da0
=>        63  2930277104  da0  MBR  (1.4T)
           63        1985       - free -  (993K)
         2048  2930274081    1  (null)  (1.4T)
   2930276129        1038       - free -  (519K)

$ mount -t ntfs /dev/da0s1 /mnt/goflex
mount: /dev/da0s1: Operation not supported by device
$ mount -t msdosfs /dev/da0s1 /mnt/goflex
mount_msdosfs: /dev/da0s1: Invalid argument
$ mount.exfat -o ro /dev/da0s1 /mnt/goflex
FUSE exfat 1.3.0
ERROR: exFAT file system is not found.

Obviously doing something wrong.
Hints?

Thanks,

Gary