Creating a cad model from Liggghts Simulation

Hi I want to do cfd analysis of a pebble bed reactor for this I need random packing of spheres in a rectangular canister. For this I performed a Liggghts simulation to create a particle bed I have the particle position text file. How can I use this to create a Cad model . I want to use that in open foam . From some where I read that I have to write a c++ code for this .how can I do that Can somebody help?