You'll need three 3.5 mm jacks to run a 5.1 setup (6 channels - 3x2). The laptop has one 3.5 mm combo jack (stereo + mic). The more elegant solution is to use the HDMI port to output both video and 5.1 audio channels.
Since your speaker system only supports 3.5 mm (check if you also have optical input), you can consider purchasing an HDMI Audio Extractor with 3.5mm and optical inputs which costs less than US$20.
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