The purpose of copyright law is to give a incentive to the creative arts. The term of copyright exclusivity has increased over time, but there are still many works that are no longer protected by copyright.
These classics are in the public domain.
However, the version that most of us find familiar may not closely resemble the classic telling of the fable.
Copyright protects the the expression and not the idea. So, a new retelling of a classic fable is protected by copyright.
So long as your telling of the classic fable starts from the classic fable and is independently develops how you retell the story, you’re OK.
Of course, it would be wise to avoid similarities with any Disney version.
And asking for a copyright clearance search and opinion from a lawyer that specializes in copyright law would be a good idea if you plan to make significant money from your retelling.