do not please. j is a notation electrical engineers use for i.

You may not have enough information to do this.  However, if the material has no magnetic response, then

eta = sqrt(u0/ɛ*) 

u0 is the free space permeability.

Solving this for ɛ* gives

ɛ* = u0/eta^2

You have to draw it on a complex plane. Mark the real part on x axis while imaginary part on y axis.

j is the representation for a complex quantity. it is the square root of "-1"

Dear Sudha Rajesh, 

you find formulas in literature to calculate real part of real part and imaginary part of dielectric constant from impedance data. Your doubt is how to join that two numbers with "j". 'j' is nothing but 'i'  so a+ib form will come. To represent its value in numarically, take mod value.

I hope this answer may solve your problem. 

thank you all for your valuable answers