In which era can the oldest fossils be found?

Question: In which era can the oldest fossils be found?

The oldest era is the paleozoic era which means "ancient life". The oldest officially recognized fossils are found in rocks from about 3.5 billion years ago putting them in the paleoarchean era of the archean eon. It is subdivided into six geologic periods the cambrian, ordovician, silurian, devonian, carboniferous, and permian.