I'm not 100% clear from your post exactly what you're seeking to achieve. But I think it's to upload old data from Weather Display running on a Mac into a station at weatherlink.com?
Assuming so: Weatherlink for Windows has no general 'Convert database' feature. I suspect what you're thinking of is the 'Import Database Files' option. This is specifically to import files from pre v5.1 versions of Weatherlink into later WL versions (the file format changed). This option can do nothing beyond importing the specific older-format WL files. It is not a generic database converter.
There is only one import mechanism into weatherlink.com and that accepts a single large block of text data as output from the Export Records option on the Browse menu of Weatherlink for Windows. See:
https://www.weatherlink.com/static/docs/import_instructions.pdf .
Getting the details right here (as described in the PDF) is critical to successful import. You've got to find a way of converting the WD data into the wl.com text import format. I doubt that there's any existing tool available to do this BICBW. Probably more a question for the WD forum? TBH I'm not sure this is worth the effort - if anything is wrong with the import at the first time of asking then it can be quite tricky to disentangle.
