There are more than 720 sites of the Long March in Gansu. You can travel anywhere in Gansu. The following is a red tour route, which I hope meets your requirements (mode 1 in the picture):

Day 1: Lanzhou (Eight Places in Lanzhou, Lanzhou Campaign Memorial Hall)

The next day: Gannan (Zoige Wetland Grassland, Diebu County People's Square, Chairman Mao's Statue)

Day 3: Diebu, Minxian and Tanchang (Red Education Base: On the second day, Chairman Mao's former residence, Russian conference site, Lazikou Battle Monument and Hadapu Memorial Hall? )

Day 4: Huining (the former site of the Red Army stationed in Huining, the Long March of the Red Army in victory gardens)