Yes, the bigger the second number, usually the longer the focal length.
However, you'll want to keep your 18-55 too because obviously the 55-200, 55-300 and 70-300 lenses aren't wide lenses (they are telephoto only). The smaller the first number, the wider-angle the lens is.
So for the wide shots (landscapes mainly), you'll want your 18-55. For the telephoto shots (nature, planes, 'things which are a long way away'), you'll want your zoom lens.
Nikon have a great tool here which allows you to try lenses virtually - here it is
http://imaging.nikon.com/lineup/lens/simulator/ just drag the slider along and it'll tell you what focal length you're looking at. As you will be able to see, there isn't a lot of difference between 200mm and 300mm, so I'd probably save your money and get the 55-200mm. Make sure you get the AF-S one with VR because the D3200 doesn't have an in-built focus motor. VR is handy too as it will minimise blurry shots taken at long focal lengths.
By the way, I'm thinking about picking up that lens for airshows.