Hi Shuang,
You are getting into the role of what's called a BASIS Administrator when asking about Instance Number's. Depending on your landscape each instance will be assigned a two digit number. You can access this information through your SAP GUI 7.xx console. The Dialog Ports, sapdp##, will always begin with 32 and end with the Instance Number. Your Gateway ports begin with 33 and Message Server ports start with 33.
Depending on your backend version, either NW730 or higher, your service file may need sapdp##, sapgw##, or sapms_SID in order for the SAP GUI client to connect.
Cheers,
Dan Mead