Retired an older Mac Pro and replaced it with a new Mac Mini 2018.  I want to run the same dual monitor set up (Dell 3007WFP-HC and Dell 2208WFP).  Because they both connected to the Mac Pro via a DVI cables, I bought Thunderbolt 3 to DVI adapters. 

Once connected to the Mac Mini, the smaller Dell 2208WFP can be displayed at 1680x1050 as its max scaled setting, but the 30" Dell 3007WFP-HC can now only be displayed at a max scale of 1280x800, which is too fuzzy to be useful.

To get better resolution on the 30" Dell, do I have a software setting issue or a cabling issue? 

The 3007WFP-HC does not have a HDMI port, but perhaps its better to find a HDMI to DVI adapter?