Creating a door access database

Hello, I've just started a new job and the door access system is in such a mess, and I want to clean it up. Basically each door has its own list of card numbers against users which can be downloaded as csv (and often HAS to be, for administrative purposes because the system is so clunky)

The lists are so out of date and the whole system needs cleaning up, but I can see exactly why it's gotten this bad, as it's so hard to use.

Im thinking of sorting something in Excel (or access if needed) that would collate all of this information (currently organized into sheets in a single workbook), tell me what doors a particular name or card number has access to, show me potential duplicates or misspellings, etc.

I'm thinking every time we make a change on each door we would download the csv and replace the data on the corresponding sheet, making manual entry of that data a thing of the past.

I need some pointers as it's not something I'm too familiar with doing