I would suggest Auburn, Merrylands and Lakemba. Even with those locations, Pakistanis are no way near a high minority. There arent that many places in Australia with a lot of Pakistani population, we are scattered all over. Harris Park is very desi but its mostly Indian and not many Pakistani shops in comparison.
Theres a good restaurant in Pennant Hills called Kolachi which is a fusion of Pakistani and Turkish cuisine, their Chicken tikka pizza is exactly what you can find in Pakistan, also do a really good Halwa Puri in the morning. I would suggest to eat in there as takeaway quality is very poor.
In terms of Mosque, that I know of, Rooty Hill Mosque is mostly run by Pakistanis and from last I went, were doing Khutba in Urdu.
If you are here until Ramadan, then Lakemba is the place to be as there is a food street that opens up every day after iftar with Desi and middle eastern food.It has become an icon now in Sydney with more non muslims now visiting the street during Ramadan.