you have not mentioned your current height and weight so its hard to tell how long it will take

remember that making a 6 pack is easy even if you have a belly..the main issue is to reduce the belly fat so the muscles can show up

go here first and check your daily calorie intake
http://calculators.hpathy.com/calories-need.asp

then make a diet plan based on your goal (don't go for a fad diet plan)

you can check for food calories here
http://caloriecount.about.com/

excellent website demystifying weight reduction and training
http://www.bodybuilding.com/fun/randy.htm

remember one thing that you CANNOT remove fat from a specific spot and fat goes off gradually from whole body..body puts fat on belly 1st and loses it in the last

1 hour brisk walk with some jogging and random sprint will really help you shed those extra pounds