Also, just food for thought: someone correct me if I'm wrong, but I believe this is a new old-stock Ethernet card of the comm slot type you need for a performa 630. $25 isn't that much in the grand scheme of things. Get that and set up an AppleTalk server on a PC with an Ethernet port (there are convenient turnkey VMs for doing just that) and your file transfer issues are a thing of the past. Plug the SE into the Performa and run the freely available AppleTalk bridge software and you'll even be able to extend your Ethernet network server to it.
http://www.ebay.com/itm/Farallon-EtherMac-YPN598-TP-YPN598-Comm-Slot-Network-Card-NIB-LAST-ONES/371762935087
http://www.ebay.com/itm/Farallon-EtherMac-YPN598-TP-YPN598-Comm-Slot-Network-Card-NIB-LAST-ONES/371762935087