What on earth is this?
if(!Directory.Exists("\\\\MANAGER\\Archive Documents\\" + Directory.CreateDirectory("\\\\MANAGER\\Archive Documents\\" + txtgetID.Text + " " + txtNumberB.Text + " " + txtDateB.Text)))
Directory.Exists() returns a true/false value, which you cannot add to a .Text string with any meaning. Directory.CreateDirectory does not return a string but returns a DirectoryInfo object. So how does true + .Text + DirectoryInfo make ANY sense whatsoever, let alone a result that's evaluable in an if statement?
Also, your use of string concatenation makes debugging the code very difficult. Try interpolation instead.
And your else clause doesn't make sense. If the directory doesn't exist, you "create" it, but then nothing after that. The else clause will not get executed unless the directory already exists by the time the code gets to the if statement!
string targetPath = $@"\\MANAGER\Archive Documents\{txtgetID.Text} {txtNumberB.Text} {txtDateB.Text}";
if (!Directory.Exists(targetPath))
{
Directory.Create(targetPath);
}
foreach (var file in new DirectoryInfo(sourcePath).GetFiles(fileName))
{
string targetFilepath = Path.Combine(targetPath, file.Name);
file.MoveTo(targetFilepath);
}