Power query - changing entries and Big Data

Hello, everybody.

I have CSV files that upon opening have some irregular IDs' entries (all IDs should have 17 characters but after filtering them by length I found some that had an irregular amount of characters - 14, 15, 18). 

However, when I created a Power Query, suddenly all the ride IDs became normal and other odd calculations were fixed too (like time(duration) became normal instead of 0:00:00).

Question 1: Why IDs become normal (example "326DCA34ABA1FAHHD") in PowerQuery but are in the form of "8.28E+22" upon opening? 

Question 2: I have multiple CSV files with hundreds of thousands of rows in each file, I need to repeat the same analysis steps for each one of them and create the same pivot tables. I could run the same VBA code for each one of them, but that would take a lot of time. I am just a beginner, so I am not sure whether or not I should use Data Models for that, create a connection to Power Bi, or what. 

Any help would be greatly appreciated.  🙂