The task is to find a file when you know its type (extension) but not its name, inside a large directory. The efficient tool for this is a wildcard search in the Windows File Explorer Search box using the pattern *.ext.

How wildcards work:

• The asterisk * stands for any sequence of characters (including none) — so it matches any file name whatsoever.
• Fixing the part after the dot restricts the match to one file type. Thus *.pdf returns every PDF, *.docx every Word document, and *.jpg every JPEG image, regardless of what the files are called.

You simply type the pattern into the search box at the top-right of File Explorer and press Enter; the search runs across the currently open folder and all of its subfolders, which is ideal for a large directory.

Why the other options are weaker: The dir command can list files and does accept wildcards, but it works only in Command Prompt on the current path and is far less convenient than a graphical recursive search — and the option as stated gives no pattern. Simply browsing through File Explorer manually means visually scanning possibly thousands of files, which is exactly the slow approach the wildcard search avoids. Checking the Recycle Bin is irrelevant — that only holds deleted files, not files still stored in the directory. The wildcard search with *.ext is the purpose-built solution.