Can a CD player can be converted to DVD player. Or else what best we can do with CD player?

Although CD players and DVD players share the same disc transport system, the laser and virtually all the electronics are different. A CD player cannot read DVDs although most DVD players will read and play CDs without a problem.

So, a CD player will always be a CD player and never a DVD player. The best thing to use a CD player for is to play CDs or, if it happens to be able to read and display images from a CD, then perhaps you can use it for picture viewing.