The Ni-like and Co-like X-rays emitted from laser produced Tin plasmas generated using the 1.06 mu m, 1.2 ns pulses from a Nd-YAG laser were modelled. The modelling includes the Ni-like and Co-like X-ray resonance line spectrum emitted from Sn plasma between 12 angstrom - 25 angstrom and also free-free and free-bound continuous spectrum emitted from the Zn-, Cu-, Ni-, Co- and Fe-like ions between 1 angstrom and 30 angstrom. Then, X-ray conversion efficiencies were calculated using these spectra. Maximum X-ray conversion efficiency was obtained 3.54 % at power density of 5 x 10(12) Wcm(-2) into 2 pi steradian. X-ray pulse durations were calculated spectrally integrated total X-ray emission of the Ni-like and Co-like from Sn plasmas.