I'm getting my parents their ringtone back and I need to know what kind of file to download it as.

Ok so on Fri. my mom tried to launder her phone (not a good idea!). so yesterday she got a new one and I’m trying to find her old ringtone and get it on her phone again. I found it, and I need to know what kind of file to download it as. The site is asking what brand of phone it is, and it’s just a Verizon phone. The choice of file is an Mp3 or AMR. Any ideas?