The Fokker D-II was a fairly mediocre and uninspired successor to the E-III monoplane responsible for the “Fokker Scourge” of 1915-’16. The D-III improved on it, but not enough to make it competitive with the Allied aircraft then coming into service, and it very nearly lost Fokker all the credit he had garnered with the German air services.
Visually, there is little to distinguish the two. There were very minor differences in dimensions, the main difference being that the D-II had only one machine-gun, while the D-III had two.
The models are supplied in 1:100 scale (above) and 1:200 scale (left). The wings and struts on the smaller scale models are thicker, to make them less fragile in play.
For 1:144 scale, either re-scale the 1:100 model to 69%, or the 1:200 model to 138%. If printing in FDM, I recommend scaling up from the 1:200 model, but in resin scaling down from 1:100 will work fine. I have printed the 1:100 model scaled down to 1:200 without problems in resin, though the struts are extremely thin and fragile.
The models can be bought at https://www.wargaming3d.com/product/fokker-d-ii-and-d-iii/