Can't paste anything or cd into hard drive

[Person_125]

so I just installed Ubuntu 18.04 LTS on my machine today and I disconnected my HDD so I can install it on the SSD cause I was afraid to erase the HDD data, first time installing Ubuntu without a VM btw, then when I connected the HDD again I found the two partitions in /dev as /dev/sdb1 and /dev/sdb2 so I first tried running the cd command to access the HDD but it tells me that /dev/sdb1 is not a directory, then I tried copying a directory to the HDD to back it up and paste was grayed out, what can I do to access it.

Oh and I did some searching online most of the things I read said to mount the HDD using

sudo mount /dev/sdb1 /mnt/sdb1

but I get this message:

Mount is denied because the NTFS volume is already exclusively opened.
The volume may be already mounted, or another software may use it 
which could be identified for example by the help of the 'fuser' command.

if it helps I had this hard drive partitioned on windows before 

[Sauron]

/dev files aren't folders, they are the device. Mounting it would have been the correct solution, but Ubuntu probably already mounted it for you automatically - open the file manager and check if the hdd shows up. You can also use fuser to find out what is using it, as the error message suggests.

[Person_125]

18 minutes ago, Sauron said:

/dev files aren't folders, they are the device. Mounting it would have been the correct solution, but Ubuntu probably already mounted it for you automatically - open the file manager and check if the hdd shows up. You can also use fuser to find out what is using it, as the error message suggests.

ok so I kinda fixed it and ruined it at the same time, I unmounted both partitions in file manager then mounted /dev/sdb1 to /mnt/sdb1, then I mounted /dev/sdb1 to /mnt/sdb1 too by mistake, and now I can't find the partition sdb1 and I think I overwrote it, but it doesn't matter it only had steam games, I just wanna get that partition back

[Sauron]

17 minutes ago, Person_125 said:

now I can't find the partition sdb1 and I think I overwrote it

I don't think you overwrote it, but... why did you unmount the partitions? Just reboot and let the file manager automount them...