Not enough info here to enable us to find a numerical answer. We don't know how many cars make up the train.
Suppose that c cars make up the train.
Then the number of seats on this train is 4(c-1) + 2.
Example: if there are a total of 3 cars, the # of seats is 4(2) + 2, or 10:
4 seats in the first car, 4 seats in the second car, and 2 seats in the third car.
