Decompress Base64 code from Json File?

This is the standard way Power BI encodes data created using the Enter Data interface.

As mentioned in a previous thread, you can modify this data by clicking on the gear icon next to the first applied step:

FYI, I've written a custom function to convert this sort of table into a more human-readable one. Using this function on your table results in the following (after adding #" " around the first two column names):

let
  Source = Table.FromRows(
    {
      {"BE", "BEL", "BELGIUM", "BENELUX"},
      {"LU", "LUX", "LUXEMBOURG", "BENELUX"},
      {"NL", "NLD", "NETHERLANDS", "BENELUX"},
      {"AT", "AUT", "AUSTRIA", "DACH"},
      {"CH", "CHE", "SWITZERLAND", "DACH"},
      {"DE", "DEU", "GERMANY", "DACH"},
      {"BG", "BGR", "BULGARIA", "EAST"},
      {"CZ", "CZE", "CZECH REPUBLIC", "EAST"},
      {"HR", "HRV", "CROATIA", "EAST"},
      {"HU", "HUN", "HUNGARY", "EAST"},
      {"MD", "MDA", "MOLDOVA", "EAST"},
      {"PL", "POL", "POLAND", "EAST"},
      {"RO", "ROU", "ROMANIA", "EAST"},
      {"RS", "SRB", "SERBIA", "EAST"},
      {"SK", "SVK", "SLOVAKIA", "EAST"},
      {"SI", "SVN", "SLOVENIA", "EAST"},
      {"FR", "FRA", "FRANCE", "FRANCE"},
      {"AD", "AND", "ANDORRA", "IBERIA"},
      {"ES", "ESP", "SPAIN", "IBERIA"},
      {"GI", "GIB", "GIBRALTAR", "IBERIA"},
      {"PT", "PRT", "PORTUGAL", "IBERIA"},
      {"IT", "ITA", "ITALY", "ITALY"},
      {"SM", "SMR", "SAN MARINO", "ITALY"},
      {"DK", "DNK", "DENMARK", "NORDICS"},
      {"EE", "EST", "ESTONIA", "NORDICS"},
      {"FI", "FIN", "FINLAND", "NORDICS"},
      {"LT", "LTU", "LITHUANIA", "NORDICS"},
      {"LV", "LVA", "LATVIA", "NORDICS"},
      {"NO", "NOR", "NORWAY", "NORDICS"},
      {"SE", "SWE", "SWEDEN", "NORDICS"},
      {"KZ", "KAZ", "KAZAKHSTAN", "RUSSIA"},
      {"RU", "RUS", "RUSSIA", "RUSSIA"},
      {"UA", "UKR", "UKRAINE", "RUSSIA"},
      {"GB", "GBR", "UNITED KINGDOM", "UK"},
      {"IR", "IRL", "IRELAND", "UK"},
      {"UK", "UK", "UNITED KINGDOM", "UK"},
      {"US", "USA", "UNITED STATES", "NORTH AMERICA"},
      {"CA", "CAN", "CANADA", "NORTH AMERICA"}
    },
    type table [#"2-digit" = text, #"3-digit" = text, Country = text, Market = text]
  )
in
  Source