Minecraft Dungeons: Arcade is an arcade variant of Mojang's Minecraft Dungeons. Players are awarded one collectible card per play, each collectible card representing an in-game item. A barcode is located at the top of the collectible card that, when scanned by the arcade cabinet, equips the player with the correlating item in-game.

After analyzing multiple cards, my friend and I were able to generate a range of barcodes spanning every obtainable card and match them with their in-game identification.

Every barcode begins with the letter "a" (possible to denote the first series of cards) followed by a number representing the category (0 = melee, 1 = ranged, 2 = armor, 3 = skins and 4 = pets). The two card numbers appear after the category (starting with 00). Once the card number reaches #11, the identifier starts with 0a and goes through 0z. Once all the lowercase letters are exhausted at card #37, the card number numbers are represented by an uppercase letter.

For example:

This was discovered with the help of this Reddit thread.