How an internal CD-ROM used as expternal CD-ROM for usage of mp3 player by connection speakers etc.

You can do that, but you only can use that for standard audio CD's . Because the player has only a "play" button, and can therefore not handle MP3 files without a computer.
At the rear panel of the CD player you will find a 4 pin plug that provides the left and right audio channels. Computer CD players are sold with that cable. The middle two of the four wires are earth wires, the outer two the signal wires. The CD audio signal strength is only 500 mVolt over 1 kOhm, so for speakers you require a small amplifier.
;)