The question behind this is: is the Universe infinite in size? If the Universe is infinite, there are an infinite number of stars.
If the Universe is finite, then so is the number of stars. There are roughly 100 billion stars in the Milky Way galaxy, and when we look at the Hubble telescope Deep Field imgaes to work out how many galaxies there are, there are roughly 10 trillion galaxies.
So the number of stars is 100 billion multiplied by 10 trillion, which is 100,000,000,000,000,000,000,000,000,000 stars 😀