Space is missing in the query:
cmd.CommandText = "Select * From Users" + "Where UserID = @UserID And Password = @Password";
If you DEBUG, you can see the commandText is:
Select * From UsersWhere UserID = @UserID And Password = @Password
Add space between Users & Where words.
Debugging is part of your learning. When you move step by step, you will be able to find such mistakes easily.