Is it possible to convert existing forms to card forms?

How do you convert classic to card format? Will I have to start from scratch? Thanks

It's possible to convert forms to the new layout, while editing the form on the builder, go to the settings tab, form settings section and click on the show more button, scroll a bit down until the "Form Layout" option where you need to select "Singe questions in one page". 

I hope this helps.