The value returned by objFS.GetFile(strFile).DateLastModified
is a date/time value. You can format this into a string using a formatting or conversion function:
dateLastModified = objFS.GetFile(strFile).DateLastModified
WScript.Echo FormatDateTime(dateLastModified, 2)
This will format the date/time value into a short date. How this is done depends on your current regional settings. E.g. in some cultures you will have "MM/dd/yyyy" and in other cultures "dd-MM-yyyy" etc.
You can also get complete control over the formatting by extracting the day, month and year part and putting them together into a string:
dateLastModified = objFS.GetFile(strFile).DateLastModified
WScript.Echo Day(dateLastModified) & "/" & Month(dateLastModified) & "/" & Year(dateLastModified)