Unfortunately there isn't a simple way to convert the world over. See, Pocket Edition is coded in a different language than the PC version of Minecraft, and the world files are saved differently as well.
Now that doesn't mean it's impossible, but it would be very complicated. I used to use MCEdit on my PC to load the "chunks.dat" file from a PE world, then place that world in a PC world, and save it. From what I've heard though, MCEdit doesn't work well with the newer versions of PE.
So if you're really set on transferring your worlds, I'm sure there's a way, but I don't know if it would be worth the time it would take to figure out.