On ctext.org all uses of 三處 seem to be fairly literal 'three places' and a translation to modern Chinese (gushiwen.cn) reads like this:
约定冲到山的东边，分作三处集合 ([they] decided to surge to the east side of the mountain, dividing it into three gathering places
项王与他的骑兵在三处会合了 。 (King Xiang met with his riders at [the] three places)
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