If you don't know how to do this, then you (or your company) really need to hire someone who does. Even if someone here has time to digest your requirements and produce "a conceptual model, then logical model and finally to physical model" for free (I don't!), they will not be able to do a proper job without discussing the requirements in more detail with the experts in the subject area.
I'm sure IT is the only industry where you'd see a question like this posted on a BB. Can you imagine: "I am a novice civil engineer, and have been asked to design a bridge to carry 4 lanes of traffic over a 50-foot wide river. I need to produce detailed plans. Can anyone show me how to go about it?"
Sorry if this seems a bit sarcastic. If your company is demanding that you perform a function for which you have no training or experience, that is their fault not yours.