The only two substances that are of interest to you are
$color(red)(2)"A" + ... -> color(blue)(3)"B" + ...$
and assume that it is balanced.
Now, notice that the reaction consumes
This tells you that regardless of the number of moles of
Use the molar mass of substance
$28.3 color(red)(cancel(color(black)("g"))) * "1 mole A"/(26.5color(red)(cancel(color(black)("g")))) = "1.068 moles A"$
Now all you have to do is use the aforementioned mole ratio to calculate how many moles of
$1.068 color(red)(cancel(color(black)("moles A"))) * (color(blue)(3)color(white)(a)"moles B")/(color(red)(2)color(red)(cancel(color(black)("moles A")))) = "1.602 moles B"$
Now, to find the number of molecules of
In your case, the number of molecules of
$1.602 color(red)(cancel(color(black)("moles B"))) * (6.022 * 10^(23)"molecules B")/(1color(red)(cancel(color(black)("mole B"))))$
$= color(green)(bar(ul(|color(white)(a/a)color(black)(9.65 * 10^(23)"molecules B")color(white)(a/a)|)))$
The answer is rounded to three .