Divide columns

Please provide sample data and expected outcome from that data.

There are many ways to accomplish this and variations depend on the nature of your data and expected outcome.

For example, if your data looks like:

This code

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMjQyNlGK1YEwTM3MwWwQE84wM7cAs0FMOMPcwlIpNhYA", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Column = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Column", Int64.Type}}),
    
    Split = Table.FromColumns(
        {Table.SelectRows(#"Changed Type", each Text.Length(Text.From([Column]))=4)[Column],
         Table.SelectRows(#"Changed Type", each Text.Length(Text.From([Column]))=7)[Column]},
         type table[Four=Int64.Type,Seven=Int64.Type])
in
    #"Split"

would produce: