This can be done using an “Insert Text Column” step along with a “Merge duplicate rows” step. This will merge your rows using a unique identifier and a delimiter. Here’s an example of my mock data:
Since you want your data in a single row, use the “Insert Text Column” step to create a Merge column and give it a unique value of 1.
Using the “Merge duplicate rows step” you should now be able to merge the rows in each column together using a comma delimiter and using the Merge column as the unique identifier.
The “Select columns” step is used to remove that Merge column. If you need to format your data as JSON, feel free to use additional “Insert Text Column”, “Find and Replace”, and “Combine columns” steps to further format your data. Otherwise, the “Send emails by row” step should do the trick.