Most of the freelancer sites support freelancers worldwide. However, Iran has unique work requirements that may affect whether you can register on a site. Here’s information I found on Upwork’s site about international freelancers registering on the site. You may need to apply to more than one site to see specifically what the requirements are for those wanting to register as a freelancer from within Iran. For example, I found several freelancers on freelancer.com that appear to be working from Iran.
Best of luck to you,
Laura, Staff Writer