^both of your devices(modem and the router) are capable of port forwarding. there more than one scenarios for you to open the ports. and one is that
1-Put your Router's IP Address in the Modem's DMZ (to forward all requests from modem to the router)
to Enable/Disable DMZ on the Modem (download and read the pdf manual(page 22) from http://safemanuals.com/user-guide-instructions-owner-manual/HUAWEI/ECHOLIFE%20HG510%20HOME%20GATEWAY-_E)
you might also want to forward a specific port like for torrents from the modem to the router. but I just think you have router for handling any specific port so forwarding all ports to the router are OK. and block/forward any specific port on the router instead.
to specify any port(s) to be forwarded from the Modem (use the tutorial http://portforward.com/english/routers/port_forwarding/Huawei/HG510/Echolink.htm)
2-And handle any specific port(s) to be forwarded from the router to the PC.
To forward a port from your router towards a PC (http://portforward.com/english/routers/port_forwarding/TP-Link/TL-R460/Echolink.htm)
See the settings/configuration in your Torrent client which port is it listening to, you have to use that port to be forwarded from the router towards the PC(on which you are going to use torrent client)
hope it might help