I have never hunted fox myself but always thought of fox as more of an animal you would be better off trapping rather than hunting.
Hunting any animal with a pistol makes it at least twice as hard as it does with a rifle. While it can be done, you have to be really good with the pistol and get the animal in much closer than a rifle.
Hopefully if you are going hunting to harvest the meat or the fur, rather than just going to shoot an animal so I would not recommend a 38 but rather a 22 caliber round.
You should get several responses to your post from others who are a lot more experienced with fox