I have in a few days a scientific conference and I will present my work in the form of a poster. Now I am in the process of looking for models of scientific posters, Please who can help me find some example.
See Colin Purrington's advice on designing conference posters. You can find it here: http://colinpurrington.com/tips/poster-design
For more examples than you'll ever want, see the comment above by Danny Ruijters.
(I know we frown on link-only answers here, but Purrington's pages have been very stable for a very long time, and the advice is too lengthy even to try to summarize here.)
For "offline" resources:
Senior members in your lab Unless your advisor is in their very first year, there's likely to be people in your research group that have given posters before. (And if your advisor is in their first year, they probably have given a poster in the not so distant past.) Ask them if they have an example of a poster they've given. As a bonus, you can talk to them about what worked well when they gave the poster and what went poorly.
This is particularly a good idea if your supervisor has strong opinions/ideas about what posters should be like, or how they should be formatted/structured. By using an example from your group, there's less chance your advisor will tell you to completely reformat things when they see it.
Others in your department Even if your group is new/small and there isn't a person in the group who has done a poster, there's bound to be someone (multiple people, probably) in your department who have given a poster session. Ask around to people you know to see if they have an example poster. Even if the only people you know are first-years who haven't even done a poster themselves, the senior members of their groups probably have a poster or two lying around.
Walls If you walk the corridors of most scientific research buildings looking for them, you'll notice that scientific posters are a main feature, right up there with yellowing article reprints and seminar announcements. Posters (after journal articles) are one of the primary methods of scientific communication, and after poster sessions there's not much you can do with the things, besides stick them on blank spots on the walls to insinuate to your colleagues that you're being vaguely productive. Wander the corridors of your building (or other buildings in your department or related departments) browsing the posted posters, and feel free to whip out your cell phone camera to take a reference photo if you see one you like.
If you're feeling particularly gregarious, you could even try knocking on the doors close to what you think are particularly good posters, and seeing if the person whose poster it is would mind talking about it or their science.
Lots of scientific posters (all fields) are stored at F1000 posters (https://f1000research.com/browse/posters?&selectedDomain=posters). Some of them have been presented in scientific congress. Just keep in mind that these posters have not been peer-reviewed.