Transferring course from Storyline to Rise

Well, you could do a screen capture of each slide, and insert each into an Image block in Rise. Or publish the Storyline (SL) file to Word, and then save each image in that file for use in Image blocks. 

However, from a UI/accessibility standpoint, putting images of SL slides into Rise is a horrible idea. The text wouldn't be responsive. Even worse, the text wouldn't be readable by a screen reader.  

You could transfer SL content into Rise via Interactive Storyline blocks: https://articulate.com/support/article/Rise-Use-Storyline-Blocks-to-Embed-Storyline-360-Courses

However, SL blocks are designed for inserting interactions that are more complicated than what Rise has. I think it'd be a clunky way to present static content. 

In short: If the course will be in Rise, it's best to develop it in Rise.