Place all excel files in one folder
Use following VBA Macros.
Paste it on your excel vba and run it.
There will be explorer dialog then select the folder.

Sub BatchOpenMultiplePSTFiles()
    Dim objShell As Object
    Dim objWindowsFolder As Object
    Dim strWindowsFolder As String

    'Select the specific Windows folder
    Set objShell = CreateObject("Shell.Application")
    Set objWindowsFolder = objShell.BrowseForFolder(0, "Select a Windows folder:", 0, "")

    If Not objWindowsFolder Is Nothing Then
       strWindowsFolder = objWindowsFolder.self.Path & "\"

       Call ProcessFolders(strWindowsFolder)

       'Open the windows folder
       Shell "Explorer.exe" & " " & strWindowsFolder, vbNormalFocus
   End If
End Sub

Sub ProcessFolders(strPath As String)
    Dim objFileSystem As Object
    Dim objFolder As Object
    Dim objFile As Object
    Dim objExcelFile As Object
    Dim objWorkbook As Excel.Workbook
    Dim strWorkbookName As String

    Set objFileSystem = CreateObject("Scripting.FileSystemObject")
    Set objFolder = objFileSystem.GetFolder(strPath)

    For Each objFile In objFolder.Files
        strFileExtension = objFileSystem.GetExtensionName(objFile)
        If LCase(strFileExtension) = "xls" Or LCase(strFileExtension) = "xlsx" Then
           Set objExcelFile = objFile
           Set objWorkbook = Application.Workbooks.Open(objExcelFile.Path)

           strWorkbookName = Left(objWorkbook.Name, (Len(objWorkbook.Name) - Len(strFileExtension)) -1)
           objWorkbook.ExportAsFixedFormat Type:=xlTypePDF, Filename:=strPath & strWorkbookName & ".pdf"

           objWorkbook.Close False
        End If
    Next

    'Process all folders and subfolders
    If objFolder.SubFolders.Count > 0 Then
       For Each objSubFolder In objFolder.SubFolders
           If ((objSubFolder.Attributes And 2) = 0) And ((objSubFolder.Attributes And 4) = 0) Then
              ProcessFolders (objSubFolder.Path)
           End If
       Next
    End If
End Sub

https://www.datanumen.com/blogs/2-effective-methods-to-batch-convert-multiple-excel-workbooks-to-pdf-files/