You can use the modem your last provider gave with the new one if you want! However I’d recommend using the router because it has a firewall which will make your computer secure!
Log into 192.168.0.1 or 192.168.1.1
Go to advance >> IP Routing
Then click NAT Virtual Server/DMZ in the NAT Options. Select the Nat Virtual Server/DMZ. Another window should open, from there Use the Rule Flavor drop down box to select Virtual Server and enter in the port forwarding details!
TCP port 4661 to connect to the eDonkey server
TCP port 4662 to connect with other clients
UDP port 4665 to send messages to other eDonkey servers