How to merge listing data with location data?

I am using WordPress 4.5.3 running Supreme Directory theme Version: 1.0.2. I am using the Open Streets API.

I have thousands of listings ready to import. The listings have the address data but not the Lat/Long, so I can’t import them. I have in another file a list of US cities with Lat/Long.

I can import the city file into the Locations of GD, but, even with the City/State/Zip/Country in multi-locations my listings are not importing because of the blank Lat/Long in the listing file.

Do you have a way for me to cross reference these files and fill in the blank Lat/Long?

Any other suggestions?

Can I import the listings by turning off the map function and then turn it on again for people to claim their listing?