We can improve the sound quality of a 64 kbps MP3. by converting it to 128 kbps (or higher)
By compressing a file at 64 kbps, audio details are eliminated and it is impossible for the computer to re-create them.
Converting MP3 from 64 kbps to 128 kbps (or more) will increase the file size without adding to the quality.
In fact, this will degrade the quality even as the conversion involves recompression, so an additional loss of quality.
Its better to keep your MP3 as is, without modification.