Connect Dell3007WFP-HC external monitor to 27-inch 2017 iMAC?

Issue: Connecting a second, external monitor (Dell 3007WFP-HC) to my 27-inch 2017 iMac -- anyone know whether connecting this monitor is possible and how to do so?

I have a Dell3007WFP-HC monitor that I can successfully connect to my MacBook Air using Apple's Mini DisplayPort to Dual-Link DVI Adapter ($99 cable). To connect it to the iMac I need an adapter that will plug into the iMac's USB-C port.

I purchased a Startek DVI-to-USB-C adapter (~$20) on recommendation from Apple tech, and that did not work. Monitor showed random lines and iMac froze. Had to unplug and reboot to restore iMac.

Next, I tried Apple's Thunderbolt3 to Thunderbolt2 adapter on the Mini DisplayPort to Dual-Link DVI adapter cable which allowed me to plug original working set-up into the iMac's USB-C port but iMac does not see the monitor and nothing happens. The Dell monitor continues to work successfully with my MacBook Air which is running the most recent Sierra OS X (12.6) and so the issue has to be related to the monitor connections on the iMAC.

The Dell3007WFP-HC monitor has native resolution capability of 2560x1600 pixels at 60Hz and has a Dual Link DVI-D with HDCP ready connector.