You will need to un-thread the ball from the C pillar. The new hatch strut will come with a new ball end.

The original ones had the cup swedged onto the ball making it non-removable.

 

 

You'll need a thin profile open ended wrench, apologies I don't know the size, something like 10 or 11mm? or just grind down a cheapo regular wrench.

The replacement ball stud screws should come with the pnew pneumatic lifts.