Unrecognized date format

I received a file that has dates listed as yyyymmdd and I can't get excel to recognize this format as a date so I can do date calculations on them.

Here is what I've tried:
Under "format cells -> number -> date" I tried a few different formats and just get "#######" back which is logical since they aren't serial numbers.

I also tried: "format cells -> number -> custom" input a new type of date format of yyyy/mm/dd and when I apply the new format to my column i just get "##########" back.

What am I missing? I have 190K rows so would rather not have to do a calculation to create the date but if that is the only way to do it I will....

Thoughts? Thanks!