Three Kingdoms: I Conquer the World with Modern Weapons

Modern weapons + System storage space + carving out a territory + inventions and innovations + making money through business + unifying the realm

The protagonist, Lin Feng, unexpectedly transmigrates to a parallel world at the end of the Eastern Han dynasty. With the modern weapons gifted by the System, he carves out a domain of his own. Using his modern knowledge, he invents and manufactures weapons, then takes advantage of the System's portable storage space to transport large quantities of goods and sell them for a profit, funding further inventions. In the end, he unifies the realm.