it depends on how you want to do transfer.
it is 30 minutes driving from gerona and about 1 hour from barcelona.
train goes from barcelona, but not from gerona airport.
taxi from gerona about €50, form barcelona €120.

Hi, could you tell me how much approx the train would cost from barcelona to pineda de mar

train ticket would be around€5 each. it is not that expensive.
have a look here for some more information.