For these kind of operations ideally use Power Query: Paste this code into Power Query's editor
let
Source = Table.FromRows (
Json.Document (
Binary.Decompress (
Binary.FromText (
"i45WMlTSUXIE4gilWJ1oJSMgywmII8E8YyDLGYijlGJjAQ==",
BinaryEncoding.Base64
),
Compression.Deflate
)
),
let
_t = ( ( type nullable text ) meta [ Serialized.Text = true ] )
in
type table [ index = _t, #"Col 1" = _t, #"Col N" = _t ]
),
#"Changed Type" = Table.TransformColumnTypes (
Source,
{ { "index", Int64.Type }, { "Col 1", type text }, { "Col N", type text } }
),
#"Unpivoted Other Columns" = Table.UnpivotOtherColumns (
#"Changed Type",
{ "index" },
"Attribute",
"Value"
)
in
#"Unpivoted Other Columns"

But to do the same in DAX use this:
Table =
GENERATE (
DISTINCT ( Atlahua[index] ),
UNION (
CALCULATETABLE ( DISTINCT ( Atlahua[Col 1] ) ),
CALCULATETABLE ( DISTINCT ( Atlahua[Col N] ) )
)
)
