How to get drive id to get the Preview of thumbnail in SP Online

Microsoft has moved recently the thumbnail previews to below URL it seems

https://contosa.sharepoint.com/_api/v2.1/drives/b!VGp7pTD04UKFFtBxC1Z86EZgQRFXsm9AnYthfHIzY61Tjn1hsCRiTqJ5pIMWmEof/items/01NYYIJQCS3QKDII3W3VBLDKXASZRYVZQJ/thumbnails/0/c144x96/content?prefer=noredirect%2Cclosestavailablesize&cb=%22%7B3414DC52%2D7623%2D42DD%2DB1AA%2DE096638AE609%7D%2C3%22

Here my question is where to get this drive id ?b!VGp7pTD04UKFFtBxC1Z86EZgQRFXsm9AnYthfHIzY61Tjn1hsCR

what is this cb denoting?

Thanks in Advance