You can start a 30 day free trial, which unlocks:
The time remaining in your trial is displayed in workspaces and boards
Once your trial expires your organization will be downgraded to the Free plan. If you are over the object limit when the plan downgrades, you will need to delete board objects before you can create any more.
You can only start a trial once per Organization space.
You can upgrade at any time while in the trial.