The library files should be place under \IntegrationServer\instances\default\package\WmJDBCAdapter\lib\jars\static.
Switching over DB flavor in JDBC Adapter is not easy as straight forward, changing the datasource driver name and etc. Most likely all the adapter services that you’ve developed might need to redevelop, as the connection is still pointing to the old connection. There are a lot metadata information like fieldtype changed from DB to DB in the connection that is encoded in base64, so I would said you need to test out. So far most of the time on my past experience, migrating from one DB to another DB will most likely ended up in redo the thing again, as there will be a lot of breaking parts that you’ll need to invest time to find out and troubleshoot the issue.
Good luck anyway.