Moving from comments to Answer section -
Please go through these List all Teams and List Channels documentation. It returns the unique ids of respective Teams and Channels.
Please check this code in C# to download a file, You need to create GraphServiceClient first.
GraphServiceClient graphClient = new GraphServiceClient( authProvider );
var stream = await graphClient.Me.Drive.Items["{driveItem-id}"].Content
.Request()
.GetAsync();
Please go through the Working with files in Microsoft Graph to store/download files. Please check this SDK documentation - https://learn.microsoft.com/en-us/graph/sdks/sdks-overview
Thanks,
Meghana
If the response is helpful, please click "Accept Answer" and upvote it. You can share your feedback via Microsoft Teams Developer Feedback link. Click here to escalate.