You need to make sure youve got the right folder. Make sure you go into the correct user for a start as sometimes you can find your way to the wrong user and therefore find an empty iTunes.
In the correct user it should be under a music folder and its normally called ''iTunes Media''. Grab this folder and copy & paste. So in 'Finder' Go 'Macintosh HD' -> 'User' -> 'Music' and either a ''iTunes'' or ''iTunes Media'' folder should be there to select.
To check that you've got the correct folder right click and click 'Get Info'. This will show you the size of the folder and should give you a clue as to wether you've got the right item.
When you paste the folder onto the MacBook Pro go into iTunes and click 'file'-'add to library' Find the folder and click choose. With a bit of luck all your music should start loading into iTunes
Hope this is helpful