Is this your own model that you created in Fusion 360? If so, you can boolean join the bodies into a single body using Combine. Once combined, you can then export the single body for use.
If this isn’t your file, you can use Bambu Studio to Assemble the body parts and then fix the mesh.
Open your 3mf file and go to Objects to view each body. Select all bodies, right click, and then select Merge to add all bodies into a single assembly. This basically combines everything into a single model that you can slice and print.
Once merged, you will receive an error that needs repaired.
Click Repair and let it sit for a while; it’s going to take quite a long time. Once completed, you can slice the file without error and print.
