Is it possible for teams to be saved in a datastore? What if I wanted to make an in-game crew system where you could create a team but when you leave the team saves with all your teammates still saved as well so when you join back it's all still there.
Yes.
The biggest problem is where you'll store the team. This depends on what you plan on doing with it. Can the team change? Is there a team leader? Can someone be in 1+ teams?
You might consider storing the team in the team leader's user id (along with the team name, who is in it, and any other relevant information); everyone else's datastore id could have something that means "go look for the team in the team leader's slot; their user id is ____"
If you meant a "crew" with NPCs (instead of players), then this is simple -- the player is the team leader; the crew will never be online without the player, so you don't need to store anything special for your NPCs; so you can just store the crew under the player's user ID.