I have signal strength in dBm and frequency in MHz is is possible to find the distance??
Any idea about how to do it?
There are several research papers claiming that there is no correlation between signal strength and distance. I've read it - among others - on Radio Link Quality Estimation in Wireless Sensor Networks: a Survey by Baccour.
Now, I don't think this is true - there must be a correlation, otherwise you could in principle receive wifi signals from across the world. But it is demonstrated that this dependency is overwhelmed by other factors, such as the non-uniform radiation pattern of the antenna, multi-path propagation (highly significant due to the short wavelength), scattering and path loss due to obstacles.
Of course there is a correlation between signal strength and distance! As you can see from this discussion over on Physics there is no fixed equation to tell you distance from signal strength, as you don't know output power, antenna length/ field pattern/geometry, propagation paths, etc, and in fact even things like the weather can change how well the signal propagates.
So what tools like kismet do (extensively used in wifi site surveys and security tests) is to plot signal strength along with location and use triangulation. Broadly speaking, excluding external factors, two points that have the same signal strength are likely to be equidistant from the wireless access point. Using many samples helps pin down locations pretty accurately.
All other things being equal (and that is a lot to ask!) there is indeed a relation between transmitter signal strength, distance, frequency, and receiver signal strength.
Are you trying to determine your location from WiFi signal strength? There is lots of info about this on the web.