The easiest solution would be to redo the import. Your screenshot doesn't show if the field that you're trying to combine is set as a multiple select or single select field, so confirm that it is set up as a multiple select field before redoing it.
If you're creating a new table from your import, click the column headers and set the correct field type for each column. It defaults to "Long Text" for text fields.
Otherwise, if it all looks correct, then you might need to do some troubleshooting on the original Excel sheet. How is the data laid out there? Are the different regulation data points on their own row (as in the imported table)? If so, you'll need a helper column that joins all of the regulation data points into a single cell (e.g. =JOIN(",",D1:D3) ; note that there are array formulas that can do this without you having to manually change the data range for each item, but that requires a bit more information about the spreadsheet).