Loop through each folder and then loop through each file to find file with certain keyword

I was able to figure out a way for the program to loop through the folder, but I am having trouble having it loop through the subfolders in the main directory.

Sub SearchDeviceFile()

Dim fso, fldr, fil, myfolder As Object
Dim wb As Workbook
Dim devfile As String
Dim d As String, ext, x
Dim srcPath As String, destPath As String, srcFile As String

Set fso = CreateObject("scripting.filesystemobject")
Set fldr = fso.getfolder(Dir("C:\*", vbDirectory))

srcPath = fldr & "\"
destPath = "C:\UNM1\"
ext = Array("*History(Device)*.csv")


For Each x In ext
    d = Dir(srcPath & x)
        
        Do While d <> ""
            srcFile = srcPath & d
            FileCopy srcFile, destPath & d
            d = Dir
        Loop
Next


End Sub