if you wanted the number of stars in the (observable) universe i can give you an estimation in the powers of ten but an exact number is impossible because
a) new stars are being formed virtually every minute so any answer i give you would be inaccurate by the time you publish it.
b) it is not a fault of science but due the limitations of technology that we cant actually sit and count all of the stars in the universe. and again due to (a) it would be futile because by the time we're done a billion or trillion other stars would have formed.