Oil dipstick tube rusted and broke

If that is just slid into a hole and it's broken off flush, the proper way is to remove the oil pan and push the broken part up and out. What I would try first is to run in a bolt and hope the threads cut in and grab it hard enough that you can pull the tube out by the bolt head. If you have the time, wash the tube out with a little cleaner on a cotton swab, mix up some epoxy, then use that to glue in a long bolt or metal rod. Ideally you want something with a head on it so you can tap on it to pop the tube out.