For the following statement, what is the "Prove" statement? If ABCD is a rhombus, then it is a parallelogram.

Answer: ABCD is a parallelogram

for any "if, then" statement, the "If" part is what is given to us. So we are given that "ABCD is a rhombus". The "then" is what we want to prove. We want to prove that ABCD being a rhombus somehow connects to ABCD also being a parallelogram.

note: "if, then" statements are called conditional statements. Your book most likely calls the "if" part to be the antecedent; while the "then" is the conclusion.