PHP Error - Verison problem?

HI Folks,
hope you had a Happy Thanksgiving
I can get to some of the info since I am locked, out of admin also with this error below.

I believe cart ver. is 1.50

http://www.ckbarrymores.com/CKSt0rE!/

"Call to undefined function: mysql_connect(). Please install the MySQL Connector for PHP"

My web hosting company came back with this reply.

Your site is currently using PHP 7.3. It is possible that downgrading PHP to 5.4 will resolve the issue, but you will want to rework the site's code to use the PDO Mysql extension so that it will be compatible with more current PHP versions. I've included some additional information below that you may find helpful:

I would like to know what is the best way to resolve the problem other than install a new cart.
Thank You,
Mark:smile:

You can determine the site's current Zen Cart version by inspecting the file /includes/version.php. If, as you surmise, the site is running Zen Cart 1.5.0, then the webhost's upgrade to PHP 7.3 is absolutely the underlying issue. Zen Cart, starting with v1.5.4, has converted to use the more current MySQL interface routines.

Ask your webhost to down-level your PHP version to PHP 5.4 so that your store can continue operations while you plan your upgrade from a version that was released December 30, 2011.

There will be a few other things that likely will need to be applied after the downgrade to PHP 5.4 while working on the upgrade by rebuild of the store. There were some cache and session related fixes needed back in the day to support PHP 5.4 on the older Zen Cart systems. There are a number of other security fixes as well, but temporary operation may be sufficient while truly working on the upgrade.