plz help me hws to install ios 6 in 3gs without deleted my contacts......????

Your iTunes will take a backup before upgrading your device to iOS 6. Do upgrade your iTunes to 10.7 before going in for the installation.

Once through with installation process, it will restore your device back to the state where you left. You don't have to bother about your data getting deleted.

Hope it helps. 🙂

As always, simply make sure that you have synced your contacts ( and everything else) to your computer or cloud service.

Everything should be on your computer or cloud service before attempting any update.

First of all upgrade your iTunes to 10.7. Secondly, here's a reference article for syncing your iPhone content with your computer: http://support.apple.com/kb/HT1296

Also, when you connect your device to iTunes and go ahead for the upgrade, it will automatically take a backup of your device before going in for the new iOS installation.

Alternatively, you can manually backup your device by Right Clicking the device showing in the Left Panel of the iTunes. There you get an option of 'Backup' in the Right Click Menu.

Thanks manikjain33 for acknowledging my assistance.

Glad I was able to resolve your concern. 🙂