How to animate this text????

Depending on how you want it to look, it could be as simple as precomposing it, turning the precomp 3d and then animating the precomp.

It's perfectly possible, but you have to approach it completely differently. Of course your layer styles will disappear/ look different if you just turn on 3D. It's inherent in how this works. Layer styles are always applied as the last step even after all transform operations. You may want to start by reading the AE online help on such basics. Other than that the simple answer is to pre-compose the text and enable 3D only in the parent comp without collapsed transformations or any such stuff and animate the resulting layer. If something else is required, you may need to re-create your look using AE's conventional effects, not layer styles and of course possibly more pre-composing right down to separating each layer in its own composition.

Mylenium