Open 3, export all site definitions (I believe you will have to do this one at a time), then close 3, and open 5.5 and import those definitions.
Open CS3, Site > Manage Sites > export all your site definitions (.ste files) to a flash drive or other safe location on your hard disk. Close CS3.
Open CS5.5, Site > Manage Sites > import your site definitions (.ste files).
Thank you both - got it to work and now am using 5.5 from now on. :-)
You will find 5.5 very different from CS3 - it will definitely require you to study your HTML and CSS. The day when you can get away with only working in Design view is past....