CHANGING BEND LOCATIONS ON A BOX

I have a customers model, its a basic box (5 sided open at one end). Because of the size I have to change its construction into 2 pcs.  I am stuck trying to change open corners into bends?  I have attached a model, I am trying to make top and back 1 pc and the second pc will be 'u' shaped (left right and bottom)

Thanks, Chris

SolidworksSheet Metal