I've seen many articles about the string theory and have a very simple question : I'd like to know how many Strings are in a quark or an electron?
There are a lot of different ways to get quantum field theories that look like the Standard Model in string theory. In some string theory models (such as the heterotic models), every particle that the Standard Model treats as point-like (electrons, quarks, etc) is a single elementary string. But there are other more complicated models in which the standard model particles are not built out of strings at all, but instead realized as the low energy excitations of D-branes wrapped around various kinds of singularities.
We don't know which (if any) of these models is actually correct, so we can't say with certainty that string theory predicts that an electron is made up of some number N of strings.