Exponential Growth Help - College Algebra

I missed my last math class covering this topic and I am having issues finding the right formula to use for the following problems. Any help would be greatly appreciated.

In 2006, the population of the United States reached 300,000,000 people. We heard in the news that in 1967 the population had reached 200,000,000 people. We of course wonder when the population will reach 350,000,000 or even 400,000,000. Find the function that describes the current population of the United States and use this function to determine in what year our population is expected to reach 400,000,000. According to this model when was our population 100,000,000?

and

On October 31, 2011 (Halloween), the world population reached the 7 billion mark. In reporting this news, we were told that the world population reached these milestones:
1804 1 billion people
1927 2 billion people
1959 3 billion people
1974 4 billion people
1987 5 billion people
1999 6 billion people
2011 7 billion people

Let t be the number of years after 1927. Find a function by using the population in 1927 and the population in 2011. Find the value of and the value of to 5 decimal places. Use this function to predict when the world population will reach 8 billion people.

The carrying capacity of the world is 14 billion people. According to your population function, when will we reach 14 billion people?