According to our current understanding of physics, it is not possible for any object with mass to travel at the speed of light. As a result, it would take an infinite amount of time for a spacecraft to reach Proxima Centauri, which is located approximately 4.24 light-years away from our solar system.
However, if we were to consider a hypothetical scenario where a spacecraft could travel at the speed of light, the journey time would be instantaneous from the perspective of the travelers. This is because time dilation occurs as an object approaches the speed of light, and for an observer on board the spacecraft, the journey would appear to take no time at all.
Regarding the fuel required for such a journey, traveling at the speed of light would require an infinite amount of energy. As an object with mass approaches the speed of light, its relativistic mass increases, and the energy required to accelerate it further also increases. Hence, the concept of using conventional fuel or propulsion systems for a spacecraft to reach light speed is not feasible.
It's important to note that our current technological capabilities are far from achieving such speeds, and any interstellar travel would require significant advancements in propulsion systems and energy sources beyond our current understanding.