The generation of high-order harmonics from planar molecules ${\mathrm{H}}_{\mathrm{3}}^{\mathrm{2}+}$ with different molecular configurations is studied using the numerical solution of the time-dependent Schr?dinger equation. The results show that planar molecules ${\mathrm{H}}_{\mathrm{3}}^{\mathrm{2}+}$ emit both odd and even harmonics, and the relative yields of odd and even harmonics are sensitive to orientation angles and molecular configuration. A simple method is proposed, based on the above results, to detect the position of atomic nucleus via odd and even high-order harmonic spectra. Bond lengths and angles from oriented asymmetric planar molecules can be reconstructed using odd-even harmonics at different angles. Meanwhile, probing the polycentric molecular structure in attoseconds using a high-order harmonic spectrum is helpful.