I was using windows search looking for .dat files on a 500 GB drive yesterday and it said it needs 1.4TB disk space
Bear in mind that searching only for files that have a .dat file extension at the end will give you A LOT of false positives. .dat's usage is extremely loaded and dozens of programs store their own different file format in files that have this extension, so you might end up with a bunch of .dat files that are
not wallet files!