A stabbing in the stomach is not a guaranteed lethal hit. There are many factors that play into stomach stabbings, or any stabbings in general. If the stabbing hits
major organs or blood vessels/arteries, your character can be assumed to be dead shortly.
If the knife avoids
major organs, arteries, blood vessels, and the like, then you will have to worry about other factors surrounding the actual stabbing and the environment around the victim. The factors surrounding the event can usually determine the time it will take them to die.
The character would need medical treatment of some kind pretty fast. Besides medical help, some factors to consider in evaluating the chance of survival include: the health of the person, how deep the wound is, the blade of the knife that did the stabbing may be of worth, organs injured, arteries severed, ability of the blood to clot, diseases the person may have, speed and availability of adequate medical treatment, amount of blood loss, the filth of the surrounding environment, whether or not pressure can be applied, the risk of infection due to foreign objects left behind inside the wound, etc.
That is a lot of scientific information. But, one thing to remember with stories is that the correct information does not always need to be fully prepared and stated. Depending on the medical and scientific advancement of the world in which your story takes place, you may need only a little detail and leave the rest to the imagination of the reader.
There is not a "specific" place that one can be stabbed with a sure chance of survival. But, a stabbing is survivable, while remaining highly sensitive and unstable. I think that is the answer you were looking for, even with the amount of information I kind of dropped on your lap there.

The actual outcome of your character's likelihood of survival relies entirely on your invention of that specific event.