Why not make your own custom ones and put it into the phone (ringtones, notifications or alarms)? It's not hard in Android. Just convert/crop the files you currently have into mp3 format and place into the appropriate folders.
Yeah, I'm using Android for the first time too and this was one of the first things I went to and looked up.
Using a file explorer, look for a 'Media' folder in the root directory. You should see 'Audio' in the 'Media' folder. Then 'Alarms', 'Notifications' and 'Rintones' in the 'Audio' folder. If none of them exist, simply create a new folder for whichever folders are missing.
Once that's out of the way, simply copy and paste the mp3 files into the appropriate folder you want to use them in.
Basically in the end, the paths should look like this: \Media\Audio\Alarms \Media\Audio\Notifications \Media\Audio\Ringtones