The question as you asked has no answer, as there are several different dipstick lengths, dipstick tube lengths and oil pans, so what someone comes up with here, will probably not be correct for you. Your best bet is to do an oil change as suggested, add the proper amount of oil for whatever application you have (we still don't know, because you've not bothered to tell us) and make a mark on the dipstick for full. You want specific answers, yet give very non specific information. Whatever you're working on is probably decades old, has likely had parts and maybe even whole engines swapped and so it may not even a matched bag of parts so to speak, yet you come here wanting specifics and give us nothing. Maybe you could start over and tell us what we're working on here? Maybe get specific if you want specific answers.