I need a scripter to transfer data from custom mysql web site to Wordpress site

Edited to add: Work won't start until early January. Sorry to all who filled my inbox with replies I've got an old personal site old personal site hosted my Namecheap that uses a mySQL database with many tables and columns. I've been working with a contactor who is building a new site using Wordpress. Trouble is, we're stymied as to copying data from tables/columns in the old DB into the new DB. There are tens of thousands of data cells so simply copy/paste is totally out of the question. Contractor won't try to create a script so we're at a dead end. I am not a coder and barely able to use the cli in Mac's Terminal app, so I'm not capable of creating a script or otherwise to accomplish this. I used Filemaker Pro ages ago and it had a neat feature that allowed easy transfer between two different DBs: The fields of the new one listed on one side and fields of the old one on the other. You then matched fields, press 'go' and the new database got populated. Something similar would be fantasic, and right at my level. If anyone could suggest ways for me to accomplish this, or who could work with me on an easy-to-use script (one that asks for existing DB and destination DB, then I press GO...), I'd be really very grateful. At 80 I'm trying to tie up 50 years of literary loose ends.