Provided you don't have too many blob items in your container, you can use this to output all the BlobItem inside your containerClient:
await foreach (BlobItem blobItem in containerClient.GetBlobsAsync())
{
Console.WriteLine("\t" + blobItem.Name);
}
BlobItem has a "Properties" property:
https://learn.microsoft.com/en-us/dotnet/api/azure.storage.blobs.models.blobitem?view=azure-dotnet
And "Properties" is a BlobPropertyItems class that has a "LastModified" property of type DateTimeOffset?:
https://learn.microsoft.com/en-us/dotnet/api/azure.storage.blobs.models.blobitemproperties?view=azure-dotnet#properties