I'm using internet through mobile phone, can I upgrade ubuntu the latest version by 2 or 3 parts? because connection is very slow. my current version ubuntu 10.10.
How can I split the downloads into multiple parts?
I think your best bet is to download the iso and use it as a live cd/usb drive.
See here: How to upgrade from 11.10 to 12.04 without internet without internet connection?
You'll need to incremental update from 10.10 to 11.10 first. This, unfortunately, means you'll need multiple ISOs. First, the 11.04 ISO. Then, the 11.10 iso. Then, the 12.04 ISO. You'll need to get the relevant ISOs, though, you didnt specify any specific architecture for your system.
11.04 ISO: http://releases.ubuntu.com/natty/
11.10 ISO: http://releases.ubuntu.com/oneiric/
12.04 ISO: http://releases.ubuntu.com/precise/
Then, using each of those, you should be able to follow the guide that To Do linked to