What era was earth first formed Cenozoic Mesozoic Paleozoic or Precambrian PLEASE HELP?

Answer 1

The earth first formed at the beginning of the Precambrian supereon which spans a very large period of time from 4,567 million years ago, through to 542 million years ago.

The beginning of the Precambrian where Earth formed is known as the Hadean eon, stretching from 4.7 Ga (billion years ago) and ended roughly 3.8 billion years ago.