I was trying to replace the HDD with SSD for my XPS 15 9530, but got 4 rounded screw heads at the base cover, so I can't remove the base cover now. These are star shape screw head and the metal seems too soft.

Any ideas that I can remove these 4 screws ?

And I need the size of the screws in case that I have to buy new ones to replace these rounded screws.