If you want to move leads from one campaign to another, it can be done via the following guide:
1. Make a filter view of the leads you want to move to a different campaign.
You can find help for filter view here:
Data Filter
Campaign Filter
2. Go to the filter and add an action by selecting "Actions":
3. Select action "Edit/move leads" followed by "Move leads to campaign" where you choose which campaign to move the leads to. Finally, select "Execute action":