Based on this:
ftps://username@1029.56.34.19
you are using FTPS. There is FTP, SFTP, and FTPS. Furthermore, there are two types of FTPS - implicit and explicit.
FTPS is FTP over SSL (like HTTPS). SFTP is really a form of SSH (behind the scenes an SFTP client is logging in via SSH and issuing commands).
The easiest thing for you to recommend your third party to do is to install Filezilla and then give them the URL. Alternatively you can look into FileZilla's import/export functions which may be easier for both you and the client. WinSCP will also work.
Windows does not have native FTPS or SFTP support. Just the weird way it integrates with Windows Explorer (not Internet Explorer) and the old ftp
command.