Do you mean .fbx or .fpx? Anyway, it really depends how much work you have to do to edit the materials. The two factors that are going cost time is the load process and material adjustment. With a huge 400+ asset pack, time just to bring it into Unreal could take an hour. Unreal generates basic materials automatically. It works well for simple things that just work by plugging into a texture coordinate, but I’m not sure how well it handles complicated materials. If the assets have a really complicated Material, you might be stuck adjusting it yourself. Feasible for basic adjustments like making something transparent as needed. Realistically, it could probably take a day’s work to bring in everything. Only would be more than a day if you had serious problems. For instance, Unreal only lets you import skeletal meshes with one root bone. Any skeletal meshes with more than one root bone would have to be adjusted in other 3D software like blender.