My sims 4 saved games are gone

Hi. The Sims 4 saves are stored locally in the Documents>Electronic Arts>The Sims 4>saves folder. If you had copied the entire Documents folder before you formatted (to an external HD or USB stick), just retrieve it and copy the save files back to the new saves folder (which has recreated itself in the same location).

If, on the other hand, you had not backed up the Documents folder, then sorry but you cannot recover them.