You should be able to export to an older format excel file .xls from FileMaker 7 and not need to export to csv.
But it exported only three records.
Try selecting Show All Records first. Export records exports the current found set so it is possible that there were only 3 records in your found set.
And FileMaker Pro 7 was the first version to support multiple tables in the same file. Thus, you may have more than one table from which you will need to export records.