Unless you are linked to another database via ODBC you do not use SQL in FileMaker to insert data into a table. There are, however, script steps you can assemble into a script that can do that.
However, it isn't strictly necessary to keep quotes and sales orders in separate tables. Since the data is the same in structure in most cases, you can actually keep both in the same pair of tables (main and detail), but add one more field to identify the main record as either "quote" or "sales order". In that case scripts that use Duplicate Record can duplicate the Main and detail records to create a sales order record with the same data.
Note, you don't even have to have two records for this, the same records could, in theory, function as both the quote and sales records--but most businesses want separate recors for this as the information in the quote is often modified at the time the sale is actually placed.