findstr
findstr /spin /c:"string" [files]
The parameters have the following meanings:
S = recursive Subfolders
P = skip non-Printable characters
I = case Insensitive
N = print line Numbers
And the string to search for is the bit you put in quotes after /c:
C:> dir /B | findstr /R /C:"[mp]"
Use findstr in Windows with following command line structure:
findstr [/I] [/S] "substring" "regex_file_name"
/I Case-insensitive search.
/S Search files in subfolders recursively.