Hello Please show me how I connect my IPad to IPhone 3GS through Personal Hotspot as wifi modem?

From the iPhone User Manual, here's how to start your personal hotspot. You must have this feature enabled from your cellular carrier - it is generally not free.

I just went through this for a friend using Verizon.

We had to call Verizon to activate the "Personal Hotspot".

Once they activated it, they assigned a temporary password to connect to the Hotspot.

We turned the Hotspot on and it then showed up as an availablel network when the iPad was looking for a wi-fi connection.

On the iPad, we put in the password and connected to the Hotspot.

Obviously you need to have good cell reception on your iPhone so the Hotspot can relay the connection to the iPad.

Not sure about other services then Verizon but should be similar.

iOS: Understanding Personal Hotspot

http://support.apple.com/kb/HT4517

Use Bluetooth to tether your iPhone, iPod touch, or iPad

http://www.macworld.com/article/1159258/bluetooth_tethering.html

How to Connect an iPad to an iPhone Via Bluetooth Tethering

http://techtips.salon.com/connect-ipad-iphone-via-bluetooth-tethering-25472.html

 Cheers, Tom 😉