The DL-3500 has a "DTE" type serial port and the SLC-5/03 has a "DTE" type serial port, so you need a null-modem serial cable like the 1747-CP3 to connect them.
If you have a cable that can connect to the SLC-5/03 Channel 0 serial port and go online with the controller from your PC, then it's the correct pinout to connect to the DL-3500.
Usually the DL-3500 is used to connect the other way; for a PC or something with a DF1 port to initiate messages to DH+ nodes.
It can work the other way, too. The PanelView needs to address the DH+ address of the DL-3500 as though it was the SLC controller. The DL-3500 will pass that command through to the serial port and the SLC should reply to it.
You mention having a 1784-PCMK card but you do not describe which network you are connected to. If you have plugged a 1784-PCM4 cable into the SLC-5/03's Channel 1 Data-Highway 485 port, I don't think you will be able to "bridge through" to browse the DH+ network to which the PanelView is connected. I'm not certain about that, but I'd be skeptical.
Change the cable, describe the Node Addresses you have assigned to the PanelView and the DL-3500, and don't worry about the 1784-PCMK.