Need information about employee permit

It's only possible to convert a Dependent Pass if the employer can successfully prove no Malaysian can do the job. So a lot depends on what is your professional area.

How much time will it take to convert dependent pass to EP?

Do I need to exit malaysia for EP? If yes,how many days do I need to stay outside malaysia approximately?

It's exactly the same process as for your wife's EP application apart from the calling visa (no need to leave as You will have arrived on a Calling Visa when on a DP) . So 10-15 working days for application process.

But usually it's quite a struggle for trailing Spouses to get approved unless in area such as IT software engineering. Jobs with supervisory roles aren't given to foreigners. So no middle management roles are likely to be approved.

If you have job offer it would be best to pursue that directly and get an EP and not try and  exchange a DP in the first instance.

Immigration are cracking down on foreign labour generally so there is no guarantee you will be able to work.