What is required to convert 78rpm records to mp3 format?

Yes you can easily do this by many ways . Use your PC using the sound recorder to record . Now convert the same file to the format required for the player -MP3.
You can also use any players with recording facility or even your mobile phone- voice recorder- to do the job and transfer.

No, the PD-6070 can only record to .wav format

Try using this program

http://www.wav-mp3.com/voc-to-mp3.htm

Your getting a format error because the format of the song,video,etc
you are trying to play is not the format needed by your MP3 player to
play the song,video,etc.
Always check in your owners manual to find out what format your player
requires.
Once you have determined what the format you have (MP3,MP4,ACC,WMA,etc.)
you will need to determine what format you need for your player to play
those songs,video,etc.
If the format that you have for your songs,videos,etc is different than
the format that you need for your player to play them, then you will
have to download a format converter and convert each song,video,etc to
the format that is usable in your MP3 player.
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You can download a FREE Media format converter at this website:
http://www.formatoz.com/

You may need to use the converter if the conversion of format is required.you can download the converter from the internet.

The music file format is not supported.