The Donkey Kong Country: Tropical Freeze Walkthrough reveals the location of every KONG Letter and Puzzle Piece in the game.  Can't find one? 
IGN: Donkey Kong: Tropical Freeze for Switch Review
3-K Precarious Pendulums - Donkey Kong Country Tropical Freeze Guide - IGN
Donkey Kong Country: Tropical Freeze Guide - Collectibles: Level 03-6, Cannon Canyon
2-1 Windmill Hills - Donkey Kong Country Tropical Freeze Guide - IGN
4-5 Sea Stack Attack - Donkey Kong Country: Tropical Freeze Walkthrough - Neoseeker
3-1 Grassland Groove - Donkey Kong Country Tropical Freeze Guide - IGN
2-A Crumble Cavern - Donkey Kong Country Tropical Freeze Guide - IGN
2-B Rodent Ruckus - Donkey Kong Country Tropical Freeze Guide - IGN
3-5 Twilight Terror - Donkey Kong Country Tropical Freeze Guide - IGN
Donkey Kong Country: Topical Freeze Guide - Collectibles: Stage 4-6, Current Capers
Donkey Kong Country: Tropical Freeze Guide - Collectibles: Level 03-2, Baobab Bonanza