Power query

I have 2 columns:

The first column indicates my source and is a concatenation of the file name plus the as of date

The second column is the record number.

Here is an example:

1.  extract_093020.xls

2.  22937

My goal is to produce a third column that has the following:  Date_record number. 

Here is an example:

093020_22937

I tried this expression (below), but get  the following error:

Expression.Error: We cannot convert the value "2020-09-30" to type List.
Details:
    Value=2020-09-30
    Type=[Type]

Text.Combine( "20"&Text.Middle([Source.Name],19,2)&"-"&Text.Middle([Source.Name],15,2)&"-"&Text.Middle([Source.Name],17,2))+[Record ID]

Please hlep me know what I am doing wrong.

Thanks,