How can I get Internet on iPad 3g from iPhone.

well i haven't tried it but perhaps you could use Wifi-tethering mode with your iphone but i'm not quite sure. give it a try!

First, does your iphone iOS is higher than 4.3? as i know the wifi-tethering mode only works in iPhone iOS 4.3 or higher.

To activate Wi-Fi tethering for iOS4 follow these steps:

1. Open settings. Tap the grey settings icon on the home screen of your iPhone.
2. Choose network. Tap on "General". Tap on "Network" to open the network settings section.
3. Enable tethering. Enable tethering in iOS4 by tapping "Set up Internet Tethering". Choose either Bluetooth or USB. The Wi-Fi tethering feature with official support has been removed from the iOS, therefore for Wi-Fi tethering there is no other choice but to jailbreak.
4. Purchase a tethering package. The iPhone may prompt you to enable internet tethering for your account. This will require you to contact your wireless provider and purchase a tethering package. Once you have purchased a tethering package repeat the steps in this guide. If you are not prompted to purchase a tethering package, skip this step.

Note :Tethering with the iPhone 4 and iOS4 can be easily accomplished with the built-in tethering functionality. The built-in tethering function is both limited and requires a subscription to a tethering package with your wireless carrier. Jailbroken users can enjoy the use of tethering without a tethering package and without limitations using a great piece of software called "MyWi".