I guess first of all I should ask....have they actually been cropped; how old was he when that was done? It sounds silly to ask, but his ears do have to have been surgically cut to the right shape and length for them to be able to stand at all. There are places in Europe that do not regularly crop their dobermans. (Some folks don't know that)
You've got a pretty good chance to get them to stand. I'd start posting, definitely plan on posting for 3 months or so and see how they look at that point.
Of course, it is an individual thing; it depends on the puppy, the shape and length of the crop, if any of the ear is standing at all at this point and how (saggy tips, crease or bend in lower ear, etc.)
We have a tutorial on what we think is the best/easiest way to post ears: https://www.dobermantalk.com/ear-cro...acker-rod.html
I see 4X4 beat me to posting the link for you.
I want to emphasize that you only leave the ears down between posting for half an hour or so before you put them back up. Don't leave them down, even if they look like they're standing on their own, to see if they will stay up. Just keep posting until he is about 6 1/2 or 7 months old, and then see where you are.
Also come here with any questions you may have--there's lots of knowledgeable folks here on all aspects of dobe raising, including ears and posting difficulties.
AND.....where are your pictures????? Welcome to DT.