I would try this on a local installation... I'm not going to write the sql script for you since I'm quite busy, and I can't do this for each individual custom directory type, how far have you got with it so far?
The tables you want to look at are:
xf_thread, xf_post: to create the name and desciption of the thread & 1st post (these are core tables, since the plug-in runs off of a hidden forum)
sf_xenkingdir_thread_map: contains the address, city, zip code (postcode) and image/logo url
longitude, latitude are not stored (the address is simply fed to google maps)
What I would do if I was you, is
1) on a local test forum, install xenkingdir (get it working)
2) create some listings and watch how these tables above are populated
3) Design a sql script that can use your existing db values and populate xenkingdir on you test environment