If not custom column

Hello Shan_Drex12 

the formula has to be like this

if [#"Column 1 (scac)"]="MONO" or [#"Column 1 (scac)"]="SHEK" or [#"Column 1 (scac)"]="VTEC" then [#"Column 2 (# of days)"]*250 else [#"Column 2 (# of days)"]*35

here the complete example

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45W8vX381fSUTJVitWJVgr2cPUGcgwNwLywEFdnEM9IKTYWAA==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [#"Column 1 (scac)" = _t, #"Column 2 (# of days)" = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Column 1 (scac)", type text}, {"Column 2 (# of days)", Int64.Type}}),
    #"Added Custom" = Table.AddColumn(#"Changed Type", "Custom", each if [#"Column 1 (scac)"]="MONO" or [#"Column 1 (scac)"]="SHEK" or [#"Column 1 (scac)"]="VTEC" then [#"Column 2 (# of days)"]*250 else [#"Column 2 (# of days)"]*35)
in
    #"Added Custom"

Copy paste this code to the advanced editor in a new blank query to see how the solution works.

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Have fun

Jimmy