Here are the steps you need to follow to move a public board to a team board:
Step 1. On your Dashboard page choose the public board you want to move by clicking on the 3 dots icon (ellipsis)
Step 2. Choose the option “Move”
Step 3. Select the team that you want to move your board.
Final Step. Now click on the button “Yes, move it!” to move your public board to a team board.
Note: When moving a public board to a team board, the URL of your previous board will change. So make sure to share the new URL with your team.