How to calculate the concentration of an ACID and SALT in a buffer solutioN?

You need to use the Hendersen-Hasselbach equation for calculation of the amounts of acid and its corresponding base (the salt you are referring to) you need to take

pH = pKa + log [base]/log[acid]

You know the pH you need and the pKa of the acid.  plug those values in the equation, and determine the log ratio of base/acid.  Taking antilog of the answer will give you the molar ratio you need to weigh out for your buffer.  From there onwards you can calculate the requisite amounts of acid and base for a given molarity and volume of the buffer solution