How to solve Unclosed quotation mark after the character string

Sub blank()
        Dim cmd As System.Data.SqlClient.SqlCommand
        Dim dr As System.Data.SqlClient.SqlDataReader
        Dim cn As System.Data.SqlClient.SqlConnection
        Dim bkp_path As String
        Try
            cn = New System.Data.SqlClient.SqlConnection(DBset())
            cn.Open()
            cmd = New System.Data.SqlClient.SqlCommand("Select [BackupPath] from Owner", cn)
            dr = cmd.ExecuteReader
            While dr.Read
                bkp_path = dr(0)
            End While
        Catch ex As Exception
        End Try
        dr.Close()
        cn.Close()
        Try
            Dim t As String
            Dim d As String
            Dim m As String
            Dim y As String
            t = Date.Now.Minute.ToString + Date.Now.Hour.ToString
            d = Date.Now.Day.ToString
            m = Date.Now.Month.ToString
            y = Date.Now.Year.ToString
            Dim uniqueid As String
            uniqueid = t & d & m & y
            If cmbserver.Text = "" Or cmbdatabase.Text = "" Then
                MsgBox("Server & Database Name Should Not Blank")
                Exit Sub
            Else
                Timer1.Enabled = True
                ProgressBar1.Visible = True
                cmd = New SqlCommand("backup database " & cmbdatabase.Text.Trim & " to disk=" & bkp_path & "" & cmbdatabase.Text.Trim & "_" & uniqueid & ".bak'", con)
                con.Open()
                cmd.ExecuteNonQuery()
                con.Close()
            End If
        Catch ex As Exception
            MsgBox(ex.Message)
        End Try
End Sub