Pa___ul3 has provided the link to Renfe's main website but, for some strange reason, the local Barcelona services don't feature on it. (That why Pineda de Mar couldn't be found).
The website you need is here:
http://www.renfe.com/.../barcelona/index.html
As you'll see, the journey from Barcelona Airport to Pineda de Mar typically takes a little under 2 hours, with a change of trains at Barcelona Sants. Renfe train fares (and public transport costs around Barcelona in general) are inexpensive.
The ViaMichelin routefinder quotes the road distance from Barcelona Airport to Pineda de Mar as 74km, taking 59 minutes. Taxi fares are here:
http://www.taxibarcel...%20Tarifes%202011.pdf
Based upon that, the weekday fare (from 0800 to 2000) should be 74 x €0.90, plus a €3.10 airport supplement, making around €70 in total. The night-time & weekend fare should be 74 x €1.15, plus the airport supplement, making around €88 in total. There's also a €2 supplement for travel between midnight and 6am on Fridays, Saturdays, Sundays & public holidays, and a charge of €1 per item of luggage.
Chris