Today I found this foam insulation in my front driver side door pannel below the door lock latch, it's always loose and resisting power window glass to get down.I need to get the part as this part is not tightly fitting,Can anyone help me to get this part number or what's it called in mechanic term? 

Have a look and take some more photos in different light conditions. The part number looks to be printed into the foam to the right of a Skoda logo, but I can't quite make it out from that pic. First line of characters, 3 groups of 3; usual VW group part number format.

 

Or just fix it in place with a bit of silicone sealant or similar. 

...or just throw it away and forget about it.

Agreed - the part number is moulded into the part, but the photo isn't good enough to let me read it. Or just throw it away.

At a guess, it's 5J7 868 522 which is part 14 here: