Yes it's possible, but cassette music quality is very poor compared to LP or CD, so don't expect good quality.
You need to connect your cassette player to your PC soundcard.
Depending on the equipment, this can be either the 'line out' or 'headphone' on the cassette player and 'line in' or 'mic' on the sound card.
You also need recording software, Audacity is fine and it's free. You can download it here.
Once you have the music on the PC you can transfer it over to the iPod or burn to CD.
TBH it's fairly tedious and the results won't be great. Unless it's music that you can't get, you'd be better off buying new CD's which may well have been digitally re-mastered.
You can buy a kit for about 75 euro - incl delivery from I want One Of Those - it's called a "cassette ripper" and includes all the cables/software also works on vinyl.