gif to 3mf conversion is certainly doable, in the way it is possible to resave GIF image to 3MF format. But considering that 3MF format is used for a special kind of content (manufacturing, 3D print etc), this is far from optimal export.
The best source for 3MF format is 3D model, such as OBJ or STL format, but perhaps importing GIF is not meant as direct file to file conversion, but like importing the GIF is additional raster object (model description etc.) or something similar.
Updated: October 30, 2023