To prove that triangles are congruent using the Side-Side-Side (SSS) theorem, you need to know the lengths of all three corresponding sides of the triangles.
From the given information, the piece of information that you would need to establish to utilize SSS congruence would be:
PR = DF
This indicates that the third pair of sides of the triangles is equal, which, along with the already provided QR = EF and PR = DF, will allow you to show that the triangles are congruent by SSS.
The angles <Q = <E and <P = <D are not required for the SSS congruence proof.