How do I change song files from WMA to MP3?

[HeavenlyOne]

I posted this on the tech part of the forum, but not many people have seen it and I've received no answers, so I'm posting it here too.

My daughter and I have new generic versions of IPod.....I downloaded songs for her but format errors are coming up on the WMA songs. I need to reformat them to MP3. How do I do that?

In addition, mine player is 4GB, yet I have only 130MB of free space. This is BRAND NEW! And I got it on Ebay, and the person selling them (who is reputable, but was having issues related to having too many orders at once) is no longer a member, so I'm unable to contact them.

I cannot figure out how to delete stuff off of there, as I have no idea what's on it that's taking up all my space. Help me out here, please.