How to move MSFlows from one tenant to another?

You can export the flow from your source environment and export it into your destination environment.
When you export flow, it will download the zip file and you need to import this zip into your destination envionment.
While import, you need to some changes in flow like site URLs, connections, etc.

PowerAutomate(formerly MS FLOW) can be exporeted as package. After you save the Flow, you will have the option to export this Flow and import to different environment. While importing it will ask for connections to be used before importing to new environment.