Donc pour le sudo mount /dev/sdax /mnt, cela me met "mount: you must specify the filesystem type" 
Pour info, j'ai utilisé sda2 a la place de sdax. 
  
Je met le résultat du sudo fdisk -l de suite le temps que je me connecte à internet via mon PC portable 
EDIT: Voila: 
Disk /dev/sda: 320.1 GB, 320072933376 bytes
255 heads, 63 sectors/track, 38913 cylinders, total 625142448 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logicial/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00035135
   Device Boot     Start       End    Blocks Id System
/dev/sda1  *        2048 621135871 310566912 83 Linux
/dev/sda2      621137918 625141759   2001921  5 Extended
/dev/sda5      621137920 625141759   2001920 82 Linux swap / Solaris
                                  
Disk /dev/sdd: 7948 MB, 7948206080 bytes
81 heads, 10 sectors/track 19165 cylinders, total: 15523840 sectors
Unit = sectors of 1*512 = 512 bytes
Sector size (logicial/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000
                                   
   Device Boot     Start       End    Blocks Id System
/dev/sdd1           8192  15523839   7757824  b W95 FAT32
Disk /dev/sdc: 4057 MB, 4057989120 bytes
255 heads, 63 sectors/track 493 cylinders, total: 7925760 sectors
Unit = sectors of 1*512 = 512 bytes
Sector size (logicial/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x02a2d91b
                                   
   Device Boot     Start       End    Blocks Id System
/dev/sdc1  *        2048   7925759   3961856  c W95 FAT32 (LBA)