how to change Data Factory in Microsoft Integration Runtime COnfiguration Manager?
On the machine where your Integration Runtime is installed, you should have a file named:
C:\Program Files\Microsoft Integration Runtime\3.0\PowerShellScript\RegisterIntegrationRuntime.ps1
Running it with your domain\username as your $credential and your Key1 from ADF as your $gatewayKey will result in a re-registration, binding your local IR process to the IR identity in your new Data Factory.
Source: https://github.com/MicrosoftDocs/azure-docs/issues/7956
You can reuse an existing self-hosted integration runtime infrastructure that you already set up in a data factory. This enables you to create a linked self-hosted integration runtime in a different data factory by referencing an existing self-hosted IR (shared).
To share a self-hosted integration runtime by using PowerShell, see Create a shared self-hosted integration runtime in Azure Data Factory with PowerShell.
For a twelve-minute introduction and demonstration of this feature, watch the following video: Hybrid data movement across multiple Azure Data Factories.
For more details, refer "Sharing the self-hosted integration runtime with multiple data factories".