Virtual screening in autodock need single file of ligands which comprises the number of ligands needed to be docked. I am unable to form a single file of ligands.
For getting all ligands into a single file in *.mol2 format (required for auto dock virtual screening) there are so many software's available. try to use discovery studio analyzer/visualizer where you can import any file and convert that into any file format. The second one is maestro academic version.