Hi, for the file processing, you can use file listener. However if you have to define the order in which they need to be processed, that has to be defined inside the BPM as File Listener would pick and process as soon as the file is available.
Suggest to try out something like this:
Define a DB to accommodate all file contents (Normalised data?)
Once the file arrive, tag the data along with the file name / create separate tables for each file to store data
Have an Agent processing which can check if all data is received, and in order, you can work on its processing