Welcome to our forums, You cannot upgrade a wifi only iPad however you can purchase a wifi 3 g MiFi modem which has a battery life of around 9 hours and has built in hot spot. These are generally prepaid and can be topped up each month or longer periods if required. The other option is if you have a smart phone that supports personal hot spot then you can connect the iPad to the phone via wifi and use the phone to connect to the Internet. Be aware some carriers in USA do not allow tethering as it is called so check with your provider. Hope that helps you with your request.