How  to clear thumbnail cache in Windows 10
vUsing Disk Cleanup We can Clear thumbnail cache 
Type Disk Cleanup in Start menu or Search Box then press Enter
You will see drive selection screen select your system drive click OK
Select Only Thumbnails then click OK to delete the tumbnail cache
Click Delete Files

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2nd Method
We can clear thumbnail cache using Command Prompt
Right click command prompt Run as administrator
type this command
cd /d %userprofile%\AppData\Local\Microsoft\Windows\Explorer
Type attrib -h thumbcache_*.db and then press Enter key
Type del thumbcache_*.db and then press Enter
Restart your PC once to complete the operation