I believe the wp_acf_values table was used in version 1 or 2, not 100& sure as it has been so long since then.
Version 3 and 4 definitely use the standard postmeta table, so this is why your older posts and newer posts use different tables.
I would imagine that the version 3 plugin would have included an update script to migrate across all the data.
Can I ask you what version of ACF did it originally use, and what version does it use now?
To find a function such as
read_from_wp_acf_values, you will need to download an older version of ACF which contains the logic to use this table and then do a copy / paste into your functions.php file.
That said, It would be smarter to just migrate across the data. I would recommend that you dig through the source code of v3 and find the update.php file which contains the migration code.
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