Hello, Juthika,

If you had told us that is the reason you are going to use Mann-Kendall test it would be easier to give you a proper answer. 

At first. you could read the basics for the whole rank statistics approach in

M.Kendall, Rank Correlation Methods (1970),

a bit more fresh 

M.Hollander, and D.A. Wolfe, Nonparametric Statistical Methods, (1999),

and maybe it could be useful the paper

S.Yue, P.Pilon, and G.Caradias, Power of theMann-Kendall and Spearman's rho tests for detect-ing monotonic trends in hydrological series (2002).

Hope you will be successful,

Best wishes.

Thank you Sir, I am going to use it for trend analysis for precipitation

Thank you, Sir