I don’t think there are any guidelines because children, parents and circumstances vary so much.
It makes sense to do things gradually so your daughter is relaxed and happy. If she does a few hours with her dad now, start to increase it.
Add an overnight and see how she copes. Be guided by her reaction I guess. Going straight to 7 nights away might be too much for her to begin with. If your ex hasn’t cared for her for a week, he might find it difficult too. You all need a chance to build up your confidence.