Mount Windows Shared Drive Outside Network

I currently am able to mount a shared windows drive on my mac by using smb://pc-name/sharedvolume and it works fine.

I'm looking into being able to mount this drive when I am outside of my home network. I already have a subdomain from dyndns that I use for a VNC application. I was hoping to be able to do the same for this. I assume I'm going to need to do some port mapping, but everything I've tried doesn't work.

Any suggestions on which ports to map and how to connect to this drive? I see the SMB ports are: 137, 138, 139, and 445.