If the story is yours you should have a go at a screenplay yourself but I'd recommend a bit of research first. Look into the art of the screenwriter - I'm sure there are sites online - and once you have an initial draft have someone you trust, with experience, go over it with you.
Perhaps you're the type who needs a class room environment? Join a writer's group? A bit of study online? How about a screenwriter's forum? There must be something like that out there!
I've dramatised stories before - fairy tales and so on - but only at an amateur dramatic level, for schools and colleges. It's a fascinating exercise. Again and again I found myself having to cut out loads of narrative- the visuals make up for the words - add extra dialogue to spice up scenes - introduce new elements. Quite a challenge.
I wish you well. If you get the first one under your belt you'll have the confidence (and template?) to do more.