What are the benefits and purpose of presenting a paper in an academic conference? If i have completed all the research work and compiled a research article then why should I present that paper in a conference and not submit it to a good journal for publication ?
The answer depends on the discipline.

In many disciplines you can do both. There are conferences where you can present work that has been published in a journal (or at another conference) or that shall be published in the future.

In other disciplines, conference publications are as "valuable" (or even more prestigious) than journal publications.

To know what is the case for your discipline, talk to your advisor.