How to change the file type in a macOS file chooser depends on your version of macOS.
For macOS 12, the file chooser has an "Options" button:
Clicking "Options" will open the file filter drop-down list:
With the file filter drop-down list, choose the type of file(s) you want to open:
For Excel Import, choose "MS Excel 97/2000/XP (*.xls)" or "MS Excel 2007 XML (*.xslx)" depending on the format/name of your Excel file:
Hope this helps.