could you advice me the right way of migrate database of wordpress

so I have a some situation, I have 2 sites:

• one site is dev version and
• Second is live version of site.

Some month ago I have copied all things from Live site to dev site, and doing many changes in Dev version. and then in this time period there are added many posts, products, and also sold products on live site, how to migrate Database from Live site to dev site without losing data on dev site changes.

Sorry for such as long question . . .

Maybe does it exists some plugin for doing this task?

via Chebli Mohamed