$ sudo apt-get update
$ sudo apt-get install libsmlnj-smlnj 

libsmlnj-smlnj is installed in your system.

Make ensure the libsmlnj-smlnj package were installed using the commands given below,

$ sudo dpkg-query -l | grep libsmlnj-smlnj *

You will get with libsmlnj-smlnj package name, version, architecture and description in a table

libsmlnj-smlnj package basic information: