"Themed Collections" is a set of missions that can be challenged, which are divided by each "Expansion."
Moreover, if there are multiple variations of the same Pokémon card, please be aware that there may be specific conditions that should be met for the eligible cards for the mission, such as rarity, shiny variant, and the way to obtain them.
As for the details of the eligible card, you can confirm by tapping the card displayed within the corresponding mission.