String parsing: Extracting the filename from a URL
I used this code to extract the FileName with Extension. 

UPDATE TableName set ColumnName= right(Image_Link, CHARINDEX('/', REVERSE(ColumnName) + '/') - 1)


And this code to extract and update only FileName 

UPDATE TableName  SET ColumnName= REVERSE(SUBSTRING(REVERSE(ColumnName),CHARINDEX('.', REVERSE(ColumnName)) + 1, 999))