I would assume you mean connect from a remote 3G device to the (?)server. What server, what OS?
If you want to get 3G speeds, you would need the server to be on a 3G connection, not dialup, otherwise you would at any rate be confined to the dial up UPLOAD speed (~33K if I remember correctly).
So, short answer, 3G card on server, some way of knowing the server IP address (dyndns.org for eg), and a 3G connection on the remote side. Remote connects to internet cloud, logs onto server using VPN, ssh, FTP or whatever, and downloads. Problems? No firewall protection against unknown ip addresses, since the remote client has dynamic ip.
Option 2? ADSL on server, 3G client side. Same problems / solutions as option 1
Option 3? What is the primary access to the internet? Diginet? 64kb/128kb? more? Same as option 1 and 2 except for the server ip address (now static).
Hope that helps, otherwise PM me