How do I properly ventilate my pantry?
I'm tempted to say that venting a pantry outside could be a bad idea as I imagine it would be a very attractive smell to rodents who will find their way in.  You'd also be forcing conditioned air outside for no real reason which will just increase utility costs.

As suggested in the answer by The Evil Greenbo, two passive vents would probably do the trick just to get the air circulating, and then you could fill the exterior hole.  

If you need more airflow you could try a fan in the room, or even just leaving the door open a bit.