Adding Text to data column based on text length

Hi,Greg_Deckler .thanks for your concern about this issue.

Your answer is excellent!
And I would like to share some additional solutions below.
Hello,QELucas .I am glad to help you.
I hope you find my test below helpful, I have uploaded my test file so you can download it and see the steps in detail.
Here is my test data.

Use M code
In Power Query:
 

if Text.Length([Tracking])=6 then [Tracking] &"A1S1"
else if Text.Length([Tracking])=8 then [Tracking] &"S1"
else if Text.Length([Tracking])=10 then [Tracking]
else [Tracking]&"Error"

Use DAX code
In Power BI

use IF function or SWITCH function:

Create a calculate column:

C_RFT Tracking = 
VAR LengthOfTarcking = LEN([Tracking])
RETURN
    IF(
        LengthOfTarcking = 6, 
        [Tracking] & "A1S1",
        IF(
            LengthOfTarcking = 8,
            [Tracking] & "S1",
            IF(
                LengthOfTarcking = 10,
                [Tracking],
                [Tracking] & "Error"
            )
        )
    )

C_switch Tracking = 
VAR LengthOfTarcking = LEN([Tracking])
RETURN
SWITCH(TRUE(),
LengthOfTarcking =6,  [Tracking] & "A1S1",
LengthOfTarcking = 8,[Tracking] & "S1",
LengthOfTarcking = 10,[Tracking],
[Tracking] & "Error"
)

I hope my suggestions give you good ideas, if you have any more questions, please clarify in a follow-up reply.

Best Regards,

Carson Jian,

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