I have few serial numbers where in I need to connet for some of the line
items I have in my spreadsheet.

For Eg: If I have 123 as serial numbers and I have 3 items to connect.
Three items are a.5685 b. 9000 c. abcd.

The result should come as
Serial# Line item
123 5685
123 9000
123 abcd

This is how it should look.

I have nearly 6000 line to do like this.