If you need to move a Member to another Membership as an Admin, follow these steps:
On the Membership tab, click on the Membership to view the Members on the right side.
Click the three dots beside the Member's name, then choose "Move to another membership."
From the list, choose the new Membership and the Member will be moved to that membership.
NOTE: You should only move members to another Membership if you no longer want the Member in the existing Membership.