The password for an iPhone 3GS has been forgotten and therefor no apps may be downloaded..
Are you talking about the Apple ID password or the phone's password?
For the phone's password see: http://support.apple.com/kb/HT1212
For your Apple ID see https://appleid.apple.com
I went there, but when it resets it sends a message to an email address. Since I did not set up this phone I have not idea what the email address is. I think I may be out of luck!!!!
Try http://expresslane.apple.com to communicate with a real human being. Or email or call iTunes Store support.
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