"Contests", in the sense that this word is used on some other platforms, are expressly prohibited by Upwork TOS.
I advise you to not use the word in a job posting, as you would probably find the posting removed by Upwork.
You ARE allowed to set up a competition between freelancers if you want to, if that means you hire multiple freelancers, pay them according to your contractual agreement on Upwork, and then decide which submission you like best. You would be well within Upwork rules to tell one freelancer you like her submission the best. You could pay her a bonus if you want to. You could hire her to do additional work if you want to.
These are all normal and recommended ways of finding the best freelancer for your ongoing project from among a field of candidates.
@Jaroslaw Z wrote:
Hi, I was wondering if is possible to make a contest on Upwork. The projects would consider some drawings.
Thanks for any answer.
Oh, you mean something like: "I want ten people spending hours working for me and I'll pay only one of them"?
I'd get a parmaban if I wrote what I'm thinking of right now.