You already declared a variable of Random class so you are on a good way. You basically randomly pick 9 characters from the string of allowed characters and store them in an array. Wne you are done you just create the password string from that array:
Dim s As String = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789?!"
Dim r As New Random
Const passwordLength As Integer = 9
Dim passwordChars() As Char = New Char(passwordLength - 1) {}
Dim charIndex As Integer
For i As Integer = 0 To passwordLength - 1
charIndex = r.Next(s.Length)
passwordChars(i) = s(charIndex)
Next
Dim password As New String(passwordChars)