How find the capacitnace value for our project?

Your question does not contain sufficient detail to give an answer with calculations. I can however point you in the right direction. AS you know, capacitors do not p DC. If you are using them as filters, you will need to know the target frequency band you wish to filter. You then calculate for maximum capacitive reactance (Xc) for that frequency band. For example if you wish to filter 60Hz as we do In America, a capacitance value of .47uf provides 56,437 ohms against a 60hz signal. I have attached below a link to an Xc calculator you will find helpful. Don't forget to rate the voltage accordingly when you pick the capacatance value. I would appreciate "best answer", if this helps.