Complex sentence: The failure of Apollo 13 delayed Apollo 14 until 1971 so that modifications could be made to the spacecraft, and switched the target of the Apollo 14 mission to the Fra Mauro formation, the intended destination of Apollo 13.
Split into simpler sentences: The failure of Apollo 13 delayed Apollo 14 until 1971 so that modifications could be made to the spacecraft. The target of the Apollo 14 mission was switched to the Fra Mauro formation, the intended destination of Apollo 13.