in which folder iphone ipsw located in windows?

If you are on windows, press WinKey+R and in the run dialog box, type "%AppData%" without the quotes.
Then choose the "Roaming" folder, then "Apple Computer" and "iPhone Software Updates". That should do it for you.
OR
C:\Users\USER NAME\AppData\Roaming\Apple Computer\iTunes

If you can not see the folders, that means you need to enable show hidden folders, the tutorial is HERE