Mid 2012 Mac Pro & Metal Compliant Graphics Card, resolution problems

To make my mid 2012 Mac Pro Metal compliant I purchased a new graphics card. The card is a Radeon Pro WX 7100 with Display Output Support (@ 60Hz):

4 @ 1920x1080

4 @ 3840x2160

2 @ 5120x2880

1 @ 7680x4320

I used the cable that came with the card, Display Port to DVI-D connectors to connect to the monitor.

The good news is that it worked, once the computer started up and when I open the system prefs I can see the Metal label under the System Report, signifying that I c an now upgrade from High Sierra to Mojave.

Detail of System Report | Metal: Supported, feature set macOS GPUFamily1 v3

The problem is that I am only getting 1200 by 800 resolution.

My monitor is an Apple 30" Cinema HD Display with the capability of 2560 by 1600 resolution, which was what it was producing with the original AMD graphics card that came with the machine.

I believe the problem is the cable, that it is not providing the DVI-Dual Link ability. Whe I purchased the Radeon WX 7100 from B7H Photo it was suggested that I purchase a j5create Mini DisplayPort to 4K DisplayPort, HDMI & DVI-D Adapter.

The problem with this solution is that the adapter is a Mini-Display port connection, while the card has 4 full sized Display Ports.

It always seems to come down to two expensive devices on either side of an unwilling or incompatible adapter. Over the years, Apple's port churn has not helped. :-)

Any thoughts or speculations on how to extricate myself would be much appreciated.

Thank you.