That's an easy one. You've got your contrapositives and your converses confused.
If all ravens are black, then anything which is not black can't be a raven. And if anything that isn't black can't be a raven, all ravens must be black. The contrapositive (i.e., literally, the "opposite-way-of-putting-it") is "all-not-blacks are not-ravens", which is true.
As blackbirds (and, oh, black cats) show, the converse is false.
"If it does not exist, there is not porn of it on the Internet" is the converse of Contrapositive 34---and means roughly the same as the converse of Rule 34; it's obviously wrong.
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If all ravens are black, then anything which is not black can't be a raven. And if anything that isn't black can't be a raven, all ravens must be black.
The contrapositive (i.e., literally, the "opposite-way-of-putting-it") is "all-not-blacks are not-ravens", which is true.
As blackbirds (and, oh, black cats) show, the converse is false.
"If it does not exist, there is not porn of it on the Internet" is the converse of Contrapositive 34---and means roughly the same as the converse of Rule 34; it's obviously wrong.