Analyzing the flux of ultra-high-energy cosmic rays (UHECRs) is crucial for unraveling their production mechanisms and sources in the universe. Constructed as a hybrid detector, the Pierre Auger Observatory in Argentina is equipped to study UHECR with energies that exceed \sim (10^{17}) eV. It comprises over 1660 water Cherenkov detectors, strategically distributed across 3000 square kilometers, complemented by fluorescence detectors for enhanced observation. The first data collection phase started in 2004 and was concluded at the end of 2021, achieving extensive exposure. In this contribution, we present the findings of the energy spectrum of UHECR based on the Phase I dataset, contributing valuable insights into their origins and helping refine astrophysical propagation models. We also explore prospects for these investigations, emphasizing the AugerPrime upgrade.