For a quick test, try an online converter. For an avatar you actually want to use on stream or in VRChat, take the extra 30 minutes to run it through Blender or Unity with the VRM tools.
If your GLB is a static mesh (a statue) or has a non-humanoid rig (like a quadruped animal), the VRM conversion process will fail because the software will not know which bone to map to the "Left Hand" or "Right Foot." convert glb to vrm