Five conical harmonic beams are generated from the interaction of femtosecond mid-infrared(mid-IR) pulses at a nominal input wavelength of 1997 nm with a 2D LiNbO_3 nonlinear photonic crystal with Sierpinski fractal superlattices. The main diffraction orders and the corresponding reciprocal vectors involved in the interaction are ascertained. Second and third harmonics emerging at external angles of 23.82° and 36.75° result from nonlinearerenkov and Bragg diffractions, respectively. Three pathways of fourth-harmonic generation are observed at external angles of 14.21°, 36.5°, and 53.48°, with the first one resulting from nonlinearerenkov diffraction, and the other two harmonics are generated via different cascaded processes. Five conical harmonic beams are generated from the interaction of femtosecond mid-infrared (mid-IR) pulses at a nominal input wavelength of 1997 nm with a 2D LiNbO_3 nonlinear photonic crystal with Sierpinski fractal superlattices. The main diffraction orders and the reciprocal vectors involved in the interaction are ascertained. Second and third harmonics emerging at an internal angles of 23.82 ° and 36.75 ° result from nonlinear  erenkov and Bragg diffractions, respectively. Three pathways of fourth-harmonic generation are observed at external angles of 14.21 °, 36.5 °, and 53.48 °, with the first one resulting from nonlinear  erenkov diffraction, and the other two harmonics are generated via different cascaded processes.