You should understand this particular train station is for local public transportation only. The only way you'll get to St Louis from this station is to take the Orange Line to DFW Airport, and board a flight.
So if you take a train from Plano Texas to St Louis you're looking at about 17 hours and some odd minutes a train ticket will cost you about $87 if you use wanderu or something like that. if you travel by car you can be there in a little over 9 hours and plane tickets were only about 40 something dollars but maybe you prefer train. Hope this helps
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