Sorry for the second reply, but I can’t edit the original anymore. I just found out that the forum replies are stored as comments in the wp_comments table. 
How do you add that into the equation ?
		
	 
	
	
	
 
		
			
	
	
		
		Thank you ! It’s still overwhelming for me, but at least I have a reference to look at.
I have one question: 
All the forum posts are contained within the wp_posts table as well as other post types, pages, etc. Do  I have to transfer them to a new table first and run the conversion then, or would it be okay to run on the wp_posts table ?