No, you would need to recreate the website using the UltimateWB website builder. For some websites, we can create an import tool, to transfer data to the UltimateWB website builder, depending on the webpages/database of your website. I may be able to give more advice based on your iWeb website; what is the url, if it is online?
If it's not too many pages, it should be easy to recreate from scratch using the UltimateWB website builder, and make use of all the features, such as the responsive app to create a mobile friendly website, with fluid design (so that your website automatically reformats based on user screen size, for the best user experience).