Codes P0720 and P0722, Speed sensor

I had a check engine like reading code p0720 and p0722 but AutoZone is saying the p0720 needs replaced, however I cannot find where the sensor is. My car is so congested it's hard to see anything. However, is it just the one sensor that needs replaced or both? My speed odometer isn't working and car shifts to second but nothing higher, sometimes not even out of first.