I really need [database connection] help

Your local testing server is likely running PHP 7 or higher which doesn't support the outdated MySQL connections.  Ideally, your remote and local testing servers should use the same versions of PHP & MySQL.  To make this work, you either need to revert to an older server model like 5.6  (not very smart for security reasons) or switch to modern coding practices.  

See my reply in this related thread from 2 days ago.

https://community.adobe.com/t5/dreamweaver/connect-database/td-p/10867775

Dreamweaver got left behind a few years ago when it came to providing database connectivity/querying. It used the now out-dated and not to be used mysql function NOT the more up-to-date mysqli (improved) or PDO connection function.

The message is saying your php server is most likely using a more up-to-date version of mysql and youre trying to connect to it using Dreamweaver, which is not compatible.

You have a couple of options, either write your own connection and queries to the database, there are plenty of videos on youtube which shows you how to do this or buy into a 3rd party extension provided by a developer who has kept up with moderm workflows, which cant be said for Dreamweaver.