Upgrade from Joomla 2.x to 3.x

I have numerous hot Joomla templates on many different websites with Joomla 2.x and want to upgrade to 3.x. How do I upgrade the template after upgrading Joomla and keep the same changes that I made to the 2.x templates? Or will I have to start from scratch after upgrading Joomla?

Manual upgrade is best method.
You have to get template 3.x versions form our download section and replace files, then you need to repeat changes