Maintenance plans are stored as SSIS packages. They can be exported and saved to file system/SQL Server.
Follow the below steps:
1. Connect to Integration Services of the SQL Server that has the maintenance plans
2. Select Stored Packages --> MSDB --> Maintenance Plans
3. Right click the required maintenance plan and Select Export Package and save to File System
4. In a new server, go to Integration services and select Stored Packages --> MSDB --> Maintenance Plans
5. Select Import Package from File System (path of the saved file). The maintenance plan will get created in the new server.