You will have to check with the retailer you purchased from about their return policy, as some will not accept returns. Some retailers have a specific time window where returns are accepted, and if you exceed that time limit, then they will not longer accept your return. And finally, some retailers do accept returns but deduct a “re-shelving fee” from your refund.
In general, anything that we were able to ship to you we should be able to return for you. Check the USPS country by country list of prohibited items to be sure.