objects with cut out background

guys, can you help me? I need to put a bottomless 2d drawing into augmented reality, but I can’t. I took the drawing, cut out the background by Gimp and turned it into Fbx by paint 3d. They are two figures that I put in a single drawing (Not knowing how to make 2 different objects appear in ARCore). But when I take to Unity’s problem and can’t make it work! I just need them to appear in augmented reality and with a jagged background. But it’s hard … can you help me please ?? It’s for a college exercise !! I have a hard time understanding the problem !!

Why not just save the images as .png to preserve the transparency, and put them in the scene as sprites?