I’m assuming you already have XNALara installed and working. That program will let you export to .obj format. From there, you’d have to find a tutorial on how to get the character rigged for use in DAZ|Studio. There are plenty of those around here.
The other thing you could do is more involved but would probably give better results in the long run. Export the model from XNA to .mesh.ascii format, which can be imported into Blender with a plugin (do a web search for that). If everything worked out OK, you should get the mesh with an armature in Blender. The armature is probably useless as far as D|S is concerned, but within Blender you can prepare the mesh for export, i.e. changing tri’s to quads, making a UV map, etc. so that when you import it into D|S you’ll have an easier time getting it rigged and textured.