Starting from the last number on the right the columns are:

Ones, tens, hundreds, thousands, ten thousands, hundred thousands, millions, ten millions, hundred millions, billions, ten billions, hundred billions, trillions, ten trillions, hundred trillions, quadrillions, ten quadrillions, hundred quadrillions. Etc.

Every three times it's ones, tens, hundreds. Every fourth times you use a different multiplier (thousands, millions, billions, etc).

Ones, tens, hundreds, thousands, ten thousands, hundred thousands, millions, ten millions, hundred millions, billions, ten billions, hundred billions, trillions, ten trillions, hundred trillions, quadrillions, ten quadrillions, hundred quadrillions. Etc.

Every three times it's ones, tens, hundreds. Every fourth times you use a different multiplier (thousands, millions, billions, etc).