The repository could not be registered because there exists a registered repository with Name 'SitecoreGallery' and SourceLocation 'https://sitecore.myget.org/F/sc-powershell/api/v2'. To register another repository with Name 'Temp8abc6d53-84f8-4c41-94ae-a57636a9f92a', please unregister the existing repository using the Unregister-PSRepository cmdlet. Cannot validate argument on parameter 'Repository'. The argument is null or empty. Provide an argument that is not null or empty, and then try the command again. The specified module 'SitecoreInstallFramework' with version '2.3.0' was not loaded because no valid module file was found in any module directory.
Error states that the repository is already registered with name and source location and you need to install the specified module with mentioned version.
If you already have a repository then run the below command and update it:
After this run the below command to verify that the repository was installed successfully or not:
Get-Module SitecoreInstallFramework –ListAvailable