The problem is to find a file when you know its type (extension) but not its name, inside a large folder. The efficient tool for this is pattern matching with wildcards in the File Explorer Search box, using a query of the form *.ext.

Wildcards let a single query stand for many possible filenames:

• The asterisk * matches any sequence of characters (including none).
• So *.ext means "any filename, followed by a dot and the given extension" — matching every file of that type regardless of its name.

For example, typing *.pdf returns every PDF, and *.docx returns every Word document. You enter the pattern in the Search box at the top-right of File Explorer and press Enter; the search covers the current folder and its subfolders, which is ideal for a large directory tree.

Why the other approaches are weaker or wrong for this specific need:

• The Recycle Bin only holds files that have already been deleted; a file you are still looking for normally is not there.
• Using the dir command can list files, and dir does support wildcards, but as stated it is a bare command-line listing without the wildcard pattern that makes the search effective; it is also less convenient than a recursive graphical search over a large tree.
• Through File Explorer generically (i.e., manually browsing folder by folder) is exactly the slow, error-prone approach the wildcard search is meant to replace when the name is unknown.

Hence entering *.ext in the File Explorer Search box is the correct and most efficient method.