LJ Potential Parameters

Can anyone help me with how to find LJ potential parameters for Lammps? Suppose I want to know LJ parameters for h-BN structure simulation in lammps!

I seriously doubt that a set of Lennard-Jones parameters will create a good representation of your system. You will either need a more complex force field with explicit bonded interactions in addition, or a manybody potential with implicit directional interactions.

That said, primary place to look for force fields and potential parameters is the published literature. Please keep in mind that for a classical MD software you not only parameters for specific elements but those also need to be optimized for the kind of compound and thermodynamic conditions.