Hi. Fun question!
That depends on what kind of assumptions you make (if you crammed all
those Plutos together they might smoosh together in wierd ways), but if
we just want to compare the volumes of the Sun and Pluto we can do it
with a bit of math. I don't know what grade you are in, but this is
something you should eventually be able to do even if you can't now.

Both the Sun and Pluto are basically spheres, so they have a volume of

V=4/3 pi (d/2)^3 = amount of space the sphere takes up

Where d is the diameter of the sphere
d_sun = diameter of the sun
d_pluto=diameter of pluto
pi= is a constant about equal to 3.14
V_sun = Volume of the Sun
V_pluto = Volume of Pluto
the ^3 is just a way of saying multiply something by itself three times
2^3 = 2 x 2 x 2= 8
or
10^3 = 10 x 10 x 10 = 1,000

V_sun / V_pluto = 4/3 pi (d_sun/2)^3 / 4/3 pi (d_pluto/2)^3
=d_sun^3/d_pluto^3

You can look up the diameters of the Sun and Pluto here:

https://nssdc.gsfc.nasa.g...planetary/factsheet/
https://nssdc.gsfc.nasa.g...ctsheet/sunfact.html

d_pluto= 2,376 km
d_sun =1,390,000 km
so V_sun/V_pluto = 1,390,000^3/2,376^3
=2.69 x 10^18 /1.34 x 10^10
=2.00 x 10^8
=200,000,000

So, roughly, you could fit 200 million Plutos in the volume of the Sun
(10^6 = 1,000,000 = 1 million).

I'm taking you through all this math because that is what I had to do
to figure it out. Also, this way if someone wants to understand what I did, they can
look at the calculation.

Terry