This study presents a comprehensive chemodynamical analysis of LAMOSTJ1109+0754, a bright (V=12.8), extremely metal-poor ([Fe/H]=-3.17) star, with a strong r-process enhancement ([Eu/Fe]=+0.94{+/-}0.12). Our results are based on the 7D measurements supplied by Gaia and the chemical composition derived from a high-resolution (R~110000), high signal-to-noise ratio (S/N~60) optical spectrum obtained by the 2.4m Automated Planet Finder Telescope at Lick Observatory. We obtain chemical abundances of 31 elements (from lithium to thorium). The abundance ratios ([X/Fe]) of the light elements (Z<~30) suggest a massive Population III progenitor in the 13.4-29.5M{sun} mass range. The heavy-element (30<Z<~90) abundance pattern of J1109+075 agrees extremely well with the scaled-solar r-process signature. We have developed a novel approach to trace the kinematic history and orbital evolution of J1109+0754 with a cOsmologically deRIved timE-varyiNg Galactic poTential (the ORIENT) constructed from snapshots of a simulated Milky Way analog taken from the Illustris-TNG simulation. The orbital evolution within this Milky Way-like galaxy, along with the chemical abundance pattern, implies that J1109+0754 likely originated in a low-mass dwarf galaxy located ~60kpc from the center of the Galaxy, which was accreted ~6-7Gyr ago, and that the star now belongs to the outer-halo population.