Watching the drama "New Recruit," what is the Thousand-Ri March? How many kilometers is it?

I was discharged from the Conscripted Police, so I never did things like the Thousand-Ri March.
Do they actually walk 400km?
While carrying full combat gear?
Back in '98, in the 35th Division, I did one 40km march -> full combat gear (it was much heavier than it looks)
and one 16km march ->> making rifles.
That's all I've done.
Do they walk 400km over 10 days?
Do they sleep in tents, laying blankets on the ground?? Or do they sleep inside down sleeping bags?
Does a truck bring the meals every time?