Those are not wrong ports but I don't think many will try to perform this over the internet. SMB is not an encrypted protocol and IMHO not inherently secure to be hosted on internet either. I am not sure how are we authenticating to these shares but kerb is certainly not gona work. Netbios hosting ports 137 138 UDP and 139 TCP are renowned for security issues.
Plus CIFS natting is not going to help if multiple users are going to access this share.
I would suggest to probably consider a VPN kind of solution than performing a NAT in this specific case.