How to stop an item that has already been collected from respawning when player returns to a scene?

Hi, In my game I have a collectible which is in abundance and I want each individual collectible to not respawn if the player has already collected it and returns to the scene. For example, there might be a hundred or so of these collectibles in one scene and if the player collects one of them, leaves the scene and then returns, the one they have collect doesn't respawn but the rest do. After some research I think I'm supposed to use data serialization to store which collectibles have been collected and which haven't but I'm unsure of how to go about doing this and the concept is quite new to me. Could someone explain to me what I'm supposed to do please?

Thanks.