Is the Mississippi river the Columbia river or the Rio gran?

They are three separate rivers on the North American continent.

The Mississippi River flows north to south in the mid-west of the U.S.A., into the Gulf of Mexico .

The Rio Grande River marks the international boundary between the U.S.,A. & Mexico. It flows west ot east, into the Gulf of Mexico at a different locationto the Mississippi.

The Columbia River is in the Rockie Mountains and flows from east to west into the Pacific Ocean.