For loop to Change button color depends on the data from the database

Question

i want to change the backcolor for buttons depends on information from database, i have form has multiple buttons as the picture bellow.

I have a database table for shops (stores),There is a column in this table that contains the shop number and a column for its status : (if rented or empty)

in the form shape Each shop has a button and this button named as the number of the store number in the database How can I do for loop to Retrieve store data from the database and changes the color of the button depends on the data from the database if it is empty or rented.

this is what i tried but i'm getting this error :

Object reference not set to an instance of an object. ( on change color code ) -> btn.BackColor = Color.LightPink

this is my code :

    Dim pagingAdapter As SqlDataAdapter
    Dim pagingDS As DataSet
    Dim dt As New DataTable

    Dim sqlstring As String = "Select * FROM shops where location='G2'"

    If SQL.conn.State = ConnectionState.Open Then
        SQL.conn.Close()
    End If
    SQL.conn.Open()

    pagingAdapter = New SqlDataAdapter(sqlstring, SQL.conn)
    pagingDS = New DataSet()
    pagingAdapter.Fill(pagingDS, "shops")
    dt = pagingDS.Tables("shops")
    MsgBox(dt.Rows.Count)

    For Each row As DataRow In dt.Rows
        Dim id As Integer = row("shop_id")
        Dim state As String = row("status")
        Dim btn As Button = TryCast(Me.Controls("Button" & id), Button)

        If state = "rented" Then
            btn.BackColor = Color.LightPink
        ElseIf state = "empty" Then
            btn.BackColor = Color.LightGreen
        End If
    Next
    SQL.conn.Close()

this is the form and i have 5 more in different shapes