It depends. Mediafire does allow a separate password protection for files, but not for folders, you can check if this is the case by opening the link in your browser.
(This is an example file with downloadpassword if you wonder how it looks: **External links are only visible to Support Staff****External links are only visible to Support Staff**). Anyway if this is the case you need the password from the uploader, we can't help you with that.

If nothing shows up for your files, it's pretty sure it's about captcha's. But I can't give an example of those as they appear randomly it seems, hence why there is no anticaptcha for yet. Because it's still experimental I think.
If this is the case, do what I described above, open link in your browser to fill it in at that moment & open JD chat to contact the devs to help them create some anticaptcha if possible.