Where is my catalytic converter located?

Lets start with the symptoms. Unless the converter seriously overheated and became plugged, it's not going to prevent the engine from running. It is a part of the exhaust system, very close to the engine, and ahead of the muffler. On '96 and newer models sold in the U.S. Its operation is monitored by the Engine computer. If you have a V-6 engine, you could have two converters. If either one fails to clean the exhaust properly, the Check Engine light will turn on and there will be a stored diagnostic fault code related to "catalytic converter efficiency". The engine will still run just fine if that's all that's wrong.

Misfires, as in old and worn spark plugs, and other causes can allow way too much raw unburned fuel to go into the exhaust. THAT can cause overheating of the catalyst material until it melts and becomes plugged. Normally the Check Engine light will flash when that happens to tell you to stop the engine immediately before the converter overheats.

My best guess is the diagnosis is wrong. Converters do not overheat on their own. They overheat in response to some other problem. That problem can also cause running problems as you described. If the engine runs fine at any time, the converter is not plugged.

The Engine Computer requests a little too much fuel to go into the engine, then it switches to too little fuel. It switches back and forth a couple of times per second. When the fuel is reduced, (lean), the unburned oxygen is momentarily stored in the catalyst material. A fraction of a second later, when that extra unburned fuel shows up, it mixes with the stored oxygen and is burned, then goes harmlessly out the tail pipe. There is supposed to be fuel being burned in the converter but it's that excessive fuel that is the problem.

When the problem occurs, check for a lot of black smoke coming from the tail pipe. That is a sure sign of way too much fuel going into the engine. Next, listen to the sound of the exhaust. It should make the normal "putt-putt" sound. If the converter is plugged, it will sound more a steady, quiet hiss.

A plugged converter can cause popping back through the intake manifold from the excessive back pressure. You could indeed have that now, and a new one will allow the exhaust to flow freely and restore normal engine power. If it does, be sure to observe whether the new converter gets red hot. If it does, the cause must be corrected to avoid destroying the new converter.