Hi,
Have you checked out the following documentation: https://docs.mendix.com/howto/integration/importing-excel-documents/
This is to import data out of an excel file. If you want to do this for more excel files, you can also do that but you need to tweak your logic to allow multiple files to be uploaded.
Hi Bin Yu,
I would recommend this LearningPath and to read the additional two HowTo's.
Importing and Exporting Your Data
https://academy.mendix.com/link/paths/44/Importing-and-Exporting-Your-Data
Importing Excel document into Mendix
https://docs.mendix.com/howto/integration/importing-excel-documents/
Importing large Excel files into Mendix
https://docs.mendix.com/howto/integration/import-a-large-excel-file/
Also a great video from Ryan Mocke which is a step by step guide through the process:
Importing Excel Documents Into Your Mendix App
https://www.youtube.com/watch?v=6W_rvzxH3WA
Good luck.