You might want to refer to the discussion from another time this question was answered. https://www.researchgate.net/post/How_to_calculate_lattice_constant_from_XRD_spectrum
Joseph S Merola has given you very good reference to calculate the parameter in your question. However, an additional reference has been attached herewith. We have also calculated the similar parameters from XRD pattern of the samples; you may refer our research papers.