Hello @Shilpi Saxena,
thanks for posting his question here again. The access to the traceability matrix depend on your used Jira/R4J edition:
If you are using R4J for Jira Cloud edition: There is currently no traceability matrix (it´s in development), but you can use the coverage view. This view servers the same purpose, but allows you to have much wider purpose. Please see the documentation. You could check out the video from the Data Center edition, it works quite similar.
Best Regards, Bernhard