File conversion script needed- IIF-->CSV/EXCEL

I'm looking for an easy drag & drop tool that will automatically adjust my .iff text files to a format that my QuickBooks Online importer can easily map. Specifically, my .iif files need the following modifications: 1) 2 column headers removed. 2) New column headers created. 3) First column removed. 3) Column order changed (although I *could* solve this by using custom mapping in my import too, instead). 4) A number generated (e.g. 1, 2, 3, 4, etc.) in a column that corresponds to each unique date. For example, for every row that has the date 4/5/2021, a "1" would appear in in the corresponding column; for every row that is dated 4/8/2021, a "2" would appear." The file can be re-sorted to make this easier. 5) File saved as .CSV or EXCEL. This solution must work on a Mac. I DO NOT CURRENTLY HAVE A LICENSE OF EXCEL and prefer Apple [login to view URL] for that work. I could also use Google Sheets or LibreOffice, if needed for your solution. My ideal solution would be an AppleScript involving Numbers.app. Please type, "This will work on Mac" in your reply so I can tell who actually read through the instructions. I will exclude anyone who does not include this attention to detail. I have attached before/after examples. Thanks!