Sudo: command not found

I am totally newbie. I try to login UNIX Solaris 10 through ssh command as user then i use sudo command to login as root: sudo su - but system give me an error sudo: not found. How can i fix this problem and install ssh services for my unix.

start by typing :
which sudo
whereis sudo
Then <path>/sudo -l (are you a configured user in sudoers?...)

Because most likely, if installed - it is not in your PATH ...
And so, do a find:
cd usr; find . -name sudo -print...