We present a new determination of the smallest neutrino mixing angle ${\theta }_{13}$ and the mass-squared difference $\Delta m_{32}^2$ using a final sample of $5.55\times {10}^6$ inverse beta-decay (IBD) candidates with the final-state neutron captured on gadolinium. This sample is selected from the complete dataset obtained by the Daya Bay reactor neutrino experiment in 3158 days of operation. Compared to the previous Daya Bay results, selection of IBD candidates has been optimized, energy calibration refined, and treatment of backgrounds further improved. The resulting oscillation parameters are ${\sin }^{2}2{\theta }_{13}=0.0851\pm 0.0024$, $\Delta m_{32}^2=(2.466\pm 0.060)\times {10}^{-3}{\mathrm{eV}}^2$ for the normal mass ordering or $\Delta m_{32}^2=-(2.571\pm 0.060)\times {10}^{-3}{\mathrm{eV}}^2$ for the inverted mass ordering.