Are CD+G wav audio files + the graphics file, or MP3 + the graphics ?
Or either ?
CD+G discs don't have files on them. They're tracks, just like regular CDs. Actually, it's best if you think of CD+G this way: Regular audio discs are CD+G discs where the graphic data happens to be blank, and regular audio CD players are CD players which ignore the graphic data at the end of each frame, regardless of whether it's blank or not.
You can play a CD+G disc in a regular player, and you can play a regular audio CD in a CD+G karaoke machine. In either case, you'll hear the audio, but you won't see any picture.
If you want to see words on the screen, you have to use discs where the graphic data was included as part of the track. The links that Yotsuya provided are to discs of that type, as are the discs that Power CDG Burner creates - if you give it the graphic data. That's an important distinction. You can't buy and download the MP3 version of the Frozen karaoke disc and expect that Power CDG Burner can somehow create the CDG data on its own. You
can create your own CDG graphics, using PowerKaraoke's CDG Creator (or other similar programs - or graph paper and a hex editor), but I doubt you want to spend $99 and many hours of work when someone else has done it for you for $8.
Regarding MP3 discs, there are some professional karaoke CD players on the market which, in addition to playing CD+G, are designed to play CDG graphic data along with matching mp3 files. It's unlikely that you've purchased one of those players, as the instructions and advertising would tout the feature as a major selling point.