Pre Zordon Era

The Pre Zordon Era includes only six team's of Power Rangers that came to be sometime before the Mighty Morphin Power Rangers; also, their true identities, home planet and origin of their Ranger power's is still unknown. They each had only one Megazord, but only two of them have a sixth member including the M.M.P.R. White Ranger.

The 6th Ranger(s)
Zordon was the original owner of the Mighty Morphin White Ranger power's and was also the 6th Ranger of The Squadron Rangers, while the Green Lightning Ranger of Power Rangers Lighting was the originally a prototype 6th until his power's were upgraded to an official 6th Ranger power but doesn't have a Zord nor a Megazord of his own. Their current whereabouts are unknown as nobody knows what happened to them before 1993.

Rangers of Eltar
Since Zordon of Eltar was the Squadron Rangers 6th Ranger, it's possible that the others were also from the planet Eltar, which means that they first became a team 10,000 year's before MMPR.