In this talk, I will illustrate an alternative approach to L\"uscher's formula for extracting the nuclear force from finite volume energy levels using the plane wave basis and eigenvector continuation. We adopt the formalism of semilocal momentum-space regularized chiral nuclear force to investigate the two-nucleon energy levels in the finite volumes using plane wave basis with no reliance on the partial wave expansion. In the chiral EFT framework, the long-range one-pion-exchange interaction is included nonperturbatively. Thus, this approach works well for the smAll boxes. We compare our method with L\"uscher's formula for scattering states and bound states. We also determine the low energy constants of chiral EFT by fitting lattice QCD data at $m_\pi$=450 MeV from NPLQCD Collaboration. In the calculation, the eigenvector continuation is used to accelerate the fitting and uncertainty quantification, which also generates an easy-to-use interface to fit the upcoming lattice QCD results in the future.