Multi-agent path finding (MAPF) has been widely used for path routing of multiple robots with applications in industries like automated warehouses. MAPF consists of finding a route for each robot while avoiding collisions. Many algorithms have been deployed to address this problem, including A* algorithm. Also, multi-robot task allocation (MRTA) plays a crucial role in the efficiency of the proposed algorithm. To deal with this problem, we present a heuristic algorithm for item pickups among all the robots. In the proposed algorithm, we use a conflict avoidance method to avoid collisions between robots in the system. Regarding the workstation assignment for each robot, we develop a model called the minimum-time-based assignment rule (MTAR) to minimize the working time of the robots. The proposed algorithm shows significant reduction in time consumption and is able to find efficient task assignment between different robots.