Depends on what the desired output would be (and I can't recall what the limit is for Union query). Your best bet might be to link to the spreadsheets as tables (I would probably try to find code for this rather than manually link 100 separate sheets that might be in 100 separate workbooks). Then create one table from one linked sheet, then use code to run one append sql that loops through all the linked tables, appending to the master table you created. In future, you would want to append only new records to this table and in the same process, update that which was changed. However, given that your source data is in sheets, my guess is that it isn't structured correctly for a database anyway. It begs the question, if you want to manage the data in Access, why bother with Excel at all? Most of the time, they are incompatible.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.