Question

How would I find the volume of 30% hydrogen peroxide solution from 20mL of 3% hydrogen peroxide solution?

Answer 1

I think your post is stated awkwardly. I assume you want to dilute 30% H2O2 to make 20 mL of a 3% solution. If that is true, use the dilution formula.
c1v1 = c2v2.
30% x mL = 3% x 20 mL.
Solve for mL of 30% stuff you need to take

Answer 2

So I would multiply 3% by 20 mL which equals 0.6. Then I would divide 0.6 by 30% to get the volume of 30% hydrogen peroxide?

Answer 3

Yes, you want 2.0 mL of the 30% stuff. Bob Pursley likes to use parts.
To do it that way you have
From 30% to 3% is a dilution of 10 so you want 1 part 30% + 9 parts water. How much is 1 part?
20 mL/10 parts = 2 mL (= 1 part)
9 parts x 2 = 18 parts water. The total is 20.