Hello!
A quick search of the BPD site and I found some docs about export.
https://businessdirectoryplugin.com/docs/#admin-export
Follow those instructions to create your export of listings and categories.
Setup a test site with GD, and get a copy of the export for listings.
You can add your custom fields first too, if you like, then export to get a CSV file with all the columns.
Rearrange your data into the new column structure, and follow the GD instructions for import:
https://wpgeodirectory.com/docs/core-export/
Let us know how it goes! And we will follow up here when we have information about subscription import. Which payment gateway do you use?
Note: It is a really good idea to do a test setup on a test site to get your import working well.