i format my macbook air and installed only windows 7 ..but unable to find drivers from internet..help me

Apple provides the BootCamp drivers on the OS X install media and the BootCamp Assistant will also allow you to download the drivers. As you are using a Mac, the expectation is that you would have OS X installed. If you have only Windows 7 installed, I'm not sure how you would go about getting the drivers unless you have the OS X installation media. Keep in mind that firmware updates can only be performed within OS X. You will not be able to update your systems firmware without a working installation of OS X (even if it is on an external drive).

As with any other computer manufacturer, Apple is responsible for supplying drivers for its hardware - and it does so but in a circuitous route - through BootCamp starting with Lion. Apple supplies the drivers which are downloaded through the BootCamp application and from there you can burn a disc or have them copied to a flash drive. In other words, even if you wish to run Windows fulltime, you really need a minimal Mac installation.