How to install Virtual box guest in Ubuntu 18.04 [duplicate]

I am trying to have virtual box guest in Ubuntu 18.04 but now able to succeed.

peter@LAPTOP-UMBBINAR:~$: sudo apt-get install virtualbox-guest-additions-iso
peter@LAPTOP-UMBBINAR:~$ Reading package lists... Done
Reading: command not found
peter@LAPTOP-UMBBINAR:~$ Building dependency tree
Building: command not found
peter@LAPTOP-UMBBINAR:~$ E: Unable to locate package virtualbox-guest-additions-iso

Any idea how to run the command ?