conversion type error

I am getting a conversion type error on the red line, can someone pls help?

Code:

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Private Function GetGap() As Integer

Dim VowelNumG As Integer
Dm Vowels as string = "AEIOU"
Dim VowelIndexG as integer

        For VowelIndexG = RandomStr.Length - 1 To 0 Step -1
            Do While VowelNumG < 5 And VowelIndexG <> (RandomStr(0))
                If Vowels.Contains(RandomStr.Substring(VowelIndexG, 1).ToUpper) Then
                    VowelNumG += 1
                    If VowelNumG = 3 Then
                        'MsgBox("Third vowel is " & RandomStr.Substring(VowelIndexG, 1) & "Char number is the " & (VowelIndexG) & "in the string")
                        Return VowelIndexG
                        Exit Function
                    End If
                End If
            Loop

        Next

    End Function

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Your comparing an Integer (VowelIndexG) with a string (RandomStr(0)).

You can convert an Integer to a string with .ToString() or from a string to an integer with CInt()