I believe the easiest way to do this is to set up a proportion.
We can also rephrase this to help.
We know that 30 is 5% of the total. From here we can set up a proportion.
30/x = 5/100
3000 = 5x Cross multiply
600 = x Divide both sides by 5
600 should be the answer. To test the answer, do 30/600 and you should get 5% or .05.
Hope this helps! Be sure to message me if you have any questions!