Changing Key of Audio Premiere
One approach is to change the speed of the clip slightly.  This will change the pitch; speeds above 100% will make the pitch higher, and speeds under 100% will make the pitch lower. You can fiddle around with the percentages until the pitch matches.  Obviously the clip will visually run faster or slower as well, so hopefully you won't need to change the speed too much. If it makes the clip look funny, you may want to separate the audio track from the video track so you can just adjust the audio speed while leaving the video speed at 100%.

As for pitch vs. key, I can tell you what they mean from a musician's point of view. A "pitch" is the vibrations per second (hertz) of a note.  The more cycles per second, the higher the pitch. The word "key" has two meanings.  On a piano, each of the things you can hit is a "key".  There are white keys and black keys.  Each one has a different pitch.  The other meaning of "key" pertains to composition. The "key" a song is written in defines the scale it uses (for the most part). Songs in the key of C major or A minor will be played on all the white keys (unless there is what's called an "accidental" note, which would be one of the black keys).  Songs in the key of G major or E minor are played on all the white notes except for F# ("F sharp"), unless there are "accidental" notes.  There is a major and minor "key" for each of the 12 "keys" in a scale.