There is a QlikView converter delivered by Qlik with the product. You'll find it in the dev-hub. I have no experience of it myself, perhaps there is somebody else in the community that can share experiences??
Erik Wetterberg https://extendingqlik.upper88.com/
The tool is quite good, but I have found it to be buggy with pivot charts (I tend to unlink and fix pivots and then delete the master items). The other downside is that it can bring across lots of stuff that is useful in QlikView but not so much in Sense. In some cases I will migrate an app and then create a new app alongside it and copy and paste just the bits I want across.