What is the molarity of 10 percent NaCl?

"0.10 percent NaCl" is a concentration of sodium chloride in a solution. There are a lot of ways of expressing concentrations, but they all describe "how much of this" is in "how much of that." Percentages, such as yours, is commonly used in marketable goods, while chemists, and medical people use different ones.

0.10 percent NaCl means that for every liter of water, there is 1 gram of salt (1000:1 part ratio). That is not much: a pinch in a little more than a quart.