I will be flying from CLE to ATL to AMS to OTP. They are all KLM flights, but operated by Delta. When I get to ATL, what terminal will I be arriving in? And what terminal will I be departing from? I will be flying from ATL to AMS on a Delta operated KLM flight.

Take a look at a terminal map.

Then call up your flights as if you're taking them today. Then check tomorrow's flights to see if there is a pattern.

You will either be leaving for AMS from either terminal E or the new terminal F. Both are accessible with the tram that runs between all of the terminals.

Not to nitpick, but we are talking about concourses at ATL. Not terminals. Same but important distinction for understanding and looking/asking for directions there.

Right. ATL's nomenclature is a bit different. There are two terminals: domestic and international. They are at opposite sides of the airport and are basically only for locally arriving and leaving passengers, baggage check and retrieval, and so on.

Then there are seven concourses, which are where aircraft gates are located. Councourse T is colocated (attached) to the Domestic Terminal, but behind security. Same goes for Concourse F, attached to the International Terminal behind security. Stretched out over a mile, between T and F, are Concourses A, B, C, D, and E.

All concourses are behind security and once through security one can wander between the seven freely as they are all conveniently connected by a single underground walkway and train. Distances are long but navigation is easy peasy.