The Large Enriched Germanium Experiment for Neutrinoless double-beta Decay (LEGEND) aims to develop a phased $^{76}Ge$-based neutrinoless double beta ($0nubetabeta$) decay experimental program with a discovery potential at a half-life beyond $10^{28}$ years. The final phase of the experiment, LEGEND-1000, will house a total mass of 1 ton HPGe detectors enriched with $^{76}Ge$ to provide a total exposure of 10 ton.yr. To achieve our discovery sensitivity goal, the detectors need to be operated in a nearly background-free regime enabled by a background index of less than $1 times 10^{-5}$ cts/keV.kg.yr near the end-point energy $Q_{betabeta}$ (2039 keV). Numerous background suppression techniques have been implemented. These techniques include the use of large inverted-coaxial point-contact (ICPC) detectors with excellent energy resolution and pulse-shape discrimination capability, ultra-radiopure and low-mass components to minimize exposure as well as the active liquid-argon veto to reject backgrounds. The presented poster will discuss in detail each of the techniques used for modeling the backgrounds for LEGEND-1000.