1980 Toyota Corolla Oxygen Sensor Missing Options

[drwbns]

Hello. My 1980 Toyota Corolla failed a smog test because the emissions were too high. I've turned down the screw near the air filter and have it idling at about 900rpms. I had it up to 1500 before the smog test. The test noted that the oxygen sensor is missing. I picked one up from Autozone for $62 but the only thing I found that looked like an oxygen sensor was in the back of the catalytic convertor that looked nothing like the oxygen sensor I bought. My question is where is the oxygen sensor on the 1980 Toyota Corolla and if the part I found toward the back of the catalytic convertor is the oxygen sensor, how can I replace it? The part I found looks like it's weld has come loose because I can pull it right out of the back of the catalytic convertor and there are signs of a broken weld/heat problem. Also, the part that I bought has a plastic connection similar to some of the parts under the hood, but the part under the car doesn't have a connector, it just continues into the under body of the car. Can I just splice the wire that it's attached to and attach the new oxygen sensor? Thanks for any help.