Uploading unstructured excel data into nosql mongodb

Hi all, I have set of excel sheet shared by different customer.but the excel are ubstructured.for example one excel has column customerid the other excel has the column as custid.similarly the order of the column may change.for different customer.I need to dumb these into a nosql db.Is each get saved as seperate collection. Or how I can unify all into a one structure.I am new to nosql