I'm trying export one pipeline created in datafactory v2 or migrate to another, but not found the option,
Could you help me please
As I know, you could learn about Continuous Integration
in Azure Data Factory. You could find below statement in the Continuous integration and deployment in Azure Data Factory.
For Azure Data Factory, continuous integration & deployment means moving Data Factory pipelines from one environment (development, test, production) to another. To do continuous integration & deployment, you can use Data Factory UI integration with Azure Resource Manager templates. The Data Factory UI can generate a Resource Manager template when you select the ARM template options. When you select Export ARM template, the portal generates the Resource Manager template for the data factory and a configuration file that includes all your connections strings and other parameters. Then you have to create one configuration file for each environment (development, test, production). The main Resource Manager template file remains the same for all the environments.
More detail steps and video,just refer to the above link.
Hope it helps you.