Answer:
your answer is correct.
Explanation:
For the purpose here, we'll call the missing point on the arc through Z point X.
Essentially, you want to make ΔXYZ ≅ ΔLMN by SSS. The construction so far ensures LM ≅ MN ≅ XY ≅ YZ. By copying the length LN to XZ, you ensure the congruence of the remaining sides of the triangles.
Then ∠XYZ ≅ ∠LMN because corresponding parts of congruent triangles are congruent.
In short, XZ needs to be the same distance as LN.