Question

write the if and then the converse the inverse and the contrapositive of frogs are amphibians

Answer 1

if you are a frog, then you are amphibian

Answer 2

or "if it is a frog, then it is amphibian" or "if that creature is a frog, then it is amphibian" not really elegant in english is it?

Answer 3

but at least you have it in the form " if P then Q" so you can write all the rest.
converse is "if Q then P" which is obviously false in this case
inverse is "if not P then not Q" which is also false
converse is "if not Q, then not P" which is true in this example