VB.NET how to get a random string value

I'm making a Texas Hold Em' game and I just started rewriting it, and I ran into a problem trying to get a random string value. My string arrayCard() is 2 of spades to Ace of Diamonds and I don't know what random function I have to write because I only know how to get a random integer value = Math.Floor(Random () * 51).

CODE:

Public Class Form1

    Dim arrayCard() As String = {"2S", "3S", "4S", "5S", "6S", "7S", "8S", "9S", "10S", "11S", "12S", "13S", "14S", "2C", "3C", "4C", "5C", "6C", "7C", "8C", "9C", "10C", "11C", "12C", "13C", "14C", "2H", "3H", "4H", "5H", "6H", "7H", "8H", "9H", "10H", "11H", "12H", "13H", "14H", "2D", "3D", "4D", "5D", "6D", "7D", "8D", "9D", "10D", "11D", "12D", "13D", "14D"}

    '*_CARD & SUIT RANDOM_*
    Dim card As Integer = Equals(Rnd() * arrayCard.Length)

    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        cmdBestHand.Visible = False
        cmdBestHandPvP.Visible = False
        cmdHit.Visible = False
        cmdHitX.Visible = False
        cmdWin.Visible = False
        picHit1.Visible = False
        picHit2.Visible = False
        'Randomize()
    End Sub

    Private Function callCard()
        Do While arrayCard.Length > 0
            arrayCard(card) = Math.Floor(Rnd() * 51)
            ReDim Preserve arrayCard(card)
        Loop
        Return "-1" 'error = deck empty
    End Function

    'while my arrayCard is greater then 0
    'put random card and suit
    'call the card + suit
    'after it calls the card and suit, save that card, put it as used, and delete the card from the array
    're dim the suit and save the array as 51 cards now
    'repeat till the array = -1 then say ERROR out or cards
    'eventually Re-Loop it To be Like 2 arrays so When it equals -1 To back To 52 For a full deck
    'DO IN FUNCTION so i can call the card in the picturebox and display the RIGHT CARD

    Private Sub cmdExit_Click(sender As Object, e As EventArgs) Handles cmdExit.Click
        Application.Exit()
    End Sub

    Private Sub cmdNewGame_Click(sender As Object, e As EventArgs) Handles cmdNewGame.Click
        'arrayCard(card) = random string value
        arrayCard(card) = arrayCard(value)
        picUser.Image = My.Resources.ResourceManager.GetObject("_" & arrayCard(card))
        picUserX.Image = My.Resources.ResourceManager.GetObject("_" & arrayCard(card))
        picStart.Image = My.Resources.ResourceManager.GetObject("_" & arrayCard(card))
        picStartX.Image = My.Resources.ResourceManager.GetObject("_" & arrayCard(card))
        picStartX2.Image = My.Resources.ResourceManager.GetObject("_" & arrayCard(card))
        cmdBestHand.Visible = True
        cmdBestHandPvP.Visible = False
        cmdHit.Visible = True
        cmdHitX.Visible = False
        cmdWin.Visible = False
        txtP1.Text = arrayCard(card)
        'txtP1.Text = "The Bridge has been made. Click Best Hand to see your fate."
        txtP2.Text = "Press Player VS Player to add a 2nd Player."
    End Sub
    Private Sub cmdPvP_Click(sender As Object, e As EventArgs) Handles cmdPvP.Click
        txtPvP.Text = "Player 2"
        txtP2.Text = "The Bridge has been made. Click Best Hand to see your fate."
        picDealer.Image = My.Resources.ResourceManager.GetObject("_" & arrayCard(card))
        picDealerX.Image = My.Resources.ResourceManager.GetObject("_" & arrayCard(card))
        cmdBestHandPvP.Visible = True
    End Sub

    Private Sub cmdBestHand_Click(sender As Object, e As EventArgs) Handles cmdBestHand.Click
    End Sub

    Private Sub cmdBestHandPvP_Click(sender As Object, e As EventArgs) Handles cmdBestHandPvP.Click
    End Sub

    Private Sub cmdHit_Click(sender As Object, e As EventArgs) Handles cmdHit.Click
        picHit1.Visible = True
        picHit1.Image = My.Resources.ResourceManager.GetObject("_" & arrayCard(card))
        cmdHitX.Visible = True
        txtP1.Text = "Have you checked your hand lately? Click Best Hand to see your fate."
        txtP2.Text = "Have you checked your hand lately? Click Best Hand to see your fate."
    End Sub

    Private Sub cmdHitX_Click(sender As Object, e As EventArgs) Handles cmdHitX.Click
        picHit2.Visible = True
        picHit2.Image = My.Resources.ResourceManager.GetObject("_" & arrayCard(card))
        cmdWin.Visible = True
        txtP1.Text = "Is your hand strong? Click Best Hand to see your fate."
        txtP2.Text = "Is your hand strong? Click Best Hand to see your fate."
    End Sub

    Private Sub cmdWin_Click(sender As Object, e As EventArgs) Handles cmdWin.Click
        'determines who has better hand and winner
    End Sub
End Class