Access USB Storage remotely

I am trying to setup a 500 GB HDD as temporary NAS solution. I plugged this hdd into router's USB port and I can access it on the local network just fine. I also enabled the HTTPS and FTP (both via internet options). It shows the https address as https://12.345.567.89:0123/shares and ftp://12.345.567.89/shares. However, when I try to access this address remotely, it doesn't work.

For local access, I used

HomeBackup/USB and it worked

For remote access in the network location in windows file path, I tried using 

https://12.345.567.89:0123/shares/USB

https://12.345.567.89:0123/USB

https://12.345.567.89/USB   and none of this worked.

Router I have is - C6300v2 

Firmware- V1.03.04

What am I missing here? I completely new to all of this . Trying to get this work for last two days, but found no solutoin. Anyhelp would be greatly appreciated.

Thank you