You can find the termination button under Unit Actions > Terminate. You'll need to set the date indicating when the membership will be terminated. The system will automatically terminate the unit on the date set. Once the day of termination is set it will show an alert that the membership is set to terminate to verify the dat set. You do not need to make an extra not to allow access since the access will not be terminated until the date you entered. Also you do not need to manually deactivate every member in the unit.
You will see an Alert at the top if there is at least one member on the Unit who is enrolled in a program that takes place beyond the termination date.