Please tell me which area in Shanghai are most of the restaurant serving Halal food are located.

It is hard to find a gathering place of halal food in SH. The halal food is serve in different places.
For convenience, you are suggested to choose to live near the People's Square Station of local subway line 2. Near it, there is a restaurant called Ye Li Xia Li in the Bailian International Plaza.
Near it, the 7-days Inn at No. 79, Guizhou Road is suggested. It is a budget one.