This is because UserControl is a class and to call methods, defined in it, you must reference them with instance of the class (actual instance, not UserControl.Find).
I can suggest two options:
1. Define Find method (if you can) in code module (not in UserControl or class module). This method will become "shared" (in VB.NET terminology) or "static" (in C++/C# terminology). You will be able to call it only with its name ("Find"), but the method cannot reference UserControl and its members (this is by the same reason).
2. With some procedure call pass actual reference for the UserControl to the form. In form, declare argument as UserControl class name and on it use your method:

[In UserControl]
Load Form1
Set Form1.UserControlReference = Me
Form1.Show

[In Form1]
Private m_UCR As [UserControlClassName]

Private Property Get UserControlReference() As [UserControlClassName]

  Set UserControlReference = m_UCR
End Property

Friend Property Set UserControlReference(ByVal New_UCR As [UserControlClassName])

  Set m_UCR = New_UCR
End Property

Sub SomeMethod()

  UserControlReference.Find([arguments])
End Sub