Why do you need to change the storage? It's perfectly efficient being stored as JSON and there are no plans to change the storage behavior. There is no means of changing it without basically rewriting half the plugin. If you're not on MySQL 5.7+ it will use a TEXT column type instead of JSON column type and disable searching functionality. Beyond that it will work perfectly fine. The JSON column type is just a little more efficient at storing JSON and is required to be able to use JSON MYSQL functions against the data (used for searching).

To extract what? You aren't going to extract individual field values from a JSON string efficiently using only SQL on MYSQL 5.6 as 5.6 does not have JSON functions. It is entirely possible to do on MYSQL 5.7+ since the JSON functions exist there. MYSQL 5.6 is end-of-life since last year with extended support ending 2021. Your host needs to be moving you to 5.7 or you should start considering finding a new host (note everyone should be on PHP 7.2 and MYSQL 5.7 minimum at this point otherwise you are significantly missing out on performance and functionality).

If your host won't update your MYSQL version then your only solution for extracting a value out of a JSON string with SQL only is functions like substring. See the below documentation on various string functions.

dev.mysql.com/doc/refman/5.6/en/string-functions.html

If your host does upgrade you to MYSQL 5.7+ then see the below documentation on how to use its JSON functions.

dev.mysql.com/doc/refman/5.7/en/json-functions.html