Hatchery Den and Healing Machine

In the Blue Fox store, you can find both of these. The Healing Machine just looks like a computer screen and has a red cross emote bubble above it. The Hatchery Den can be accessed by interacting with whoever has the emote that looks like an egg. It is the storage for all the Micromon you don't currently have in your party. You can only hold 6 in your party at a time, so any you don't want to use can be stored to be taken out later within your Hatchery Den system. Each Hatchery Den keeps track of all your Micromon, so you never have to worry about remembering which town's Den you used to store which Micromon.

Both of these cost nothing to use.