Porto 6.0 adds templates builder which enables you build header, footer, block, single product, shop, etc as well as page using WPBakery, Elementor and Visual Composer. Porto 5 already had block and product layout builder. We improved their elements and combined them under new templates builder.
If you update Porto from 5.x to 6.x , it converts old blocks and product layouts automatically and moved them under Porto -> Templates Builder. So you don't need to worry about losing them.