The question of how many stars exist in the universe is a truly terrifying one when you consider what lies beyond any limit we can imagine. To begin with, an attempt to quantify in one number is meaningless because such a number would be impossible to express in terms we can comprehend. Therein lies the first of many problems however it does not stop there because nobody can even begin to quantify the number of galaxies that exist in addition to our own small Milky Way. The reason is simple we cannot see beyond a certain range.
The obvious obstacle to any attempt at defining this question is the tyranny of distance. We humans struggle to quantify distances from point to point in one small galaxy and the physical distance between any two far exceed the dimensions of any one galaxy. Humans invented a system of expressing numbers to represent exceedingly large or small quantities yet no system invented comes close to being adequate for the answer we seek.
Some suggest the universe is not infinite, this is not supportable, nor is it fully deniable because the fact remains that nobody really knows for sure. What lies beyond the reach of our telescopes will remain one of the mysteries of our life and we can only but speculate endlessly to the question of how many stars exist in our universe. This assumes of course that ours is the only universe in existence Oh dear what have I said, this is an entirely new subject of conjecture!