The problem says that there's a proportion between females and males, and this proportion is 3:2, for 3 females there are 2 males.
That means that if we divide the people into 5 equal parts, 3 parts will be female and 2 parts will be male.
Using that logic, let's divide the county people into 5 equal parts

Then each part has 352 people. As we said, 3 parts will be female, then

Therefore, there are 1056 females.
And the males will be 2 parts, then

We can also check that the males + females must be all the population:

Again, there are 1056 females in the county