The sun makes up 99.86% of the mass of the solar system. It's so big that you could squeeze 1.3 million Earth inside of it.
So, how many Earths can fit in the Sun? The answer is that it would take 1.3 million Earth to fill up the Sun. That's a lot of Earths.
The Sun makes up 99.86% of the mass of the Solar System. And it's the giant planets like Jupiter and Saturn which make the most of that remaining .14% of the Solar System.
If you'd like to do the calculation yourself, here are your numbers. The volume of the Sun is 1.412 x 10^18 km3. And the volume of the Earth is 1.083 x 10^12 km3. So if you divide the volume of the Sun by the volume of the Earth, you get 1,300,000.
Of course, the Sun is a fairly average-sized star. There are some enormous stars out there. For example, the red giant Betelgeuse has a radius of 936 times the radius of the Sun. That gives it hundreds of millions of times more volume than the Sun.