conveyor is an easy to use Blender addon that allows you to batch convert FBX, OBJ, DAE, GLB and GLTF between each other.
Clone or download the repository, and install it in Blender.
Once installed, conveyor is available in the n-panel. To use it, simply pick the input folder in which your models reside, pick their format, then select the folder in which the converted files will be saved, and the target format.
This addon is an alpha state. There might be some bugs or incomplete features. As such, don't hesitate to submit an issue report.