Issue after migrating from v7

I am having a few issues with my migration.

I copied my entire v7 directorypress to a new subdomain so I start the migration.

I used the migration tool, which did a reasonable job, but I noticed that all my custom fields were showing, but were no longer connected to the database keys. I re-created the custom fields, and linked them to their relevant keys, using the responsive theme, which brought the data in as expected.

My problem is that I now have duplicate custom fields both referencing the same data keys – how do I remove the older versions of these custom fields without deleting the data which is now linked to the new custom fields?

The screenshot may make it easier to understand.