Take the string head off. Put it on a shelf.
Buy a grass gator replacement head for your machine.
Buy a package of replacement blades while your there.
I just picked this site as an example... Grass gator at Lowes
The OP has a curved shaft trimmer...
Makes no difference.
I ran them on a cheapie homeowners Ryobi curved shaft back in the day.
Grass gator make 2 types of blades....1 with a metal serrated edge, 1 w/a plastic edge.
Buy the plastic edge.
1 thing I did learn, cuz the blades last longer than string,
you need to check the oil/lube for the shaft head more often.