Find a seam where you can use a seam ripper and undo one side.
Here is a helpful video: https://www.youtube.com/watch?v=9zlvV1tOEGo
Hi Lynne, I hope this helps you out a bit
Here's a post that might help - https://homeguides.sfgate.com/restuffing-sofa-cushions-101120.html
I would replace the foam in the cushions and cover it with upholstery batting (also called Cushion Wrap or Dacron). The foam and batting can be purchased on eBay, and comes in different stages of firmness. I hope this helps!