You're getting two different network connections that use the same connector type confused.
The 2711-T10C8 has both a DH+ port (3-pin Phoenix connector) and an RS-232 port.
It can communicate with PLCs only through the DH+ connection.
It can communicate with PanelBuilder32 or with a serial printer through the RS-232 connection.
The 1784-PCM5 cable looks like an RS-232 cable, but it's not. Way back when RS-232 was done only on 25-pin connectors, A-B used a 9-pin connector for a port called "Peer Communication Link" (PCL) which was compatible with Data Highway Plus (DH+). The 1784-PCM5 cable can connect to PLC-5 Classic controllers PCL ports, or it can use a 1784-PCM7 adapter to connect to PLC-5 Enhanced and SLC-5/04 controllers via the Mini-DIN8 round connector.
To download to this terminal, your best bet is to use a USB/RS232 converter and a straight-through serial cable connected to the RS-232 port.
The second best option is to use an ATA Flash memory card. A CompactFlash card (under 2 GB, formatted FAT16 mode) in a Type II PCMCIA carrier usually works well with any PV Standard terminal with version 3 or later firmware.