Transform from Excel to Power Querry

Hi Yonah - it appears to be largely correct, but the formula will create a confusing data type becasue 1, 2 & 3 are numbers and "" is text.  You could replace using the following options: (1) switch "" with null, or replace 1, 2, & 3 with "1", "2" or "3" - see below.  

If this does not help, could you please share the error message that you are seeing?  

if 
    (Text.Contains(Text.Start([articledescription],3), "GN ")) and [articlenumber]<>0 
    then "" 
    else if Text.Contains([articledescription], "ST#")
    then "2"
    else if Text.Contains([articledescription], "RT#")
    then "1"
    else if Text.Contains([articledescription], "PN#")
    then "3"
    else ""

if 
    (Text.Contains(Text.Start([articledescription],3), "GN ")) and [articlenumber]<>0 
    then null 
    else if Text.Contains([articledescription], "ST#")
    then 2
    else if Text.Contains([articledescription], "RT#")
    then 1
    else if Text.Contains([articledescription], "PN#")
    then 3
    else null