Steps involved to perform this operations are following:

Step #1:

Backup and export following database tables

#__categories,

#__content,

#__workflow_associations,

#__viewlevels,

#__assets

Note : #_ is presented as your site database prefix, and it is also found in configuration.php. So full table name can be abdul_content instead of #__content.

Step #2:

Now after you have updated site. Or you are migrating data to new site. Then go to phpmyadmin and import above tables. And check out the result in admin of site, for the of data imported using phpmyadmin.

Step #3:

Now if you can't see categories or content has wrong categories. Then we have to update categories id, in table #__categories in case you imported data from old database,

else create new categories from website admin, then update catid in #__content table accordingly.