Need Help Immeadiately

Okay A huge question to anyone who would love to answer this and who knows alot about iPods and computers and can explain this…I just bought a Ipod to replace my Mp3 player now I wanted to take all the music that I had on my Mp3 player and put it on my iPod but for some reason even after I send it to it and copied it and all the things I thought to do it still doesn’t work and when I plug my iPod into my computer it just says Do Not Disconnect and I’m so confused right now I’m living in the stone age and just trying to keep up so If anyone can help me right now I would love it
The General