Can I install Ubuntu 16.04 on Raspberry Pi 3 model B instead of Ubuntu mate? If you have more information please let me know !
this answer assumes that you have already searched for and found instructions for:
installing Ubuntu 16.04 on Raspberry Pi 3 model B
It also assumes that the problem you are actually trying to solve is to install a different operation system while preserving information on an existing operating system. If this is indeed your situation, I would recommend that you use a new SD card for Ubuntu 16.04 in order to preserve whatever you have on your current Ubuntu Mate installation. Then plug your SD cards into a desktop/laptop to transfer files by hand.