Create a new mail merge with type "Directory" (this was called "Catalog" in
Word 2000 and earlier).

Use your existing recipient list as the data source.

Suppose you are using 10 fields. Create a table with 1 row and 10 columns.
Insert mergefield fields for each of the fields you want, one per cell.

Merge to a new document.

Add a heading row if you want one.