In IDEA I am trying to push some commits.
I have a requirement that on remote server it looks like single action.
I click to push and see following window
I expected to see squash checkbox here but don't see it.
Please help me.
You can do it using rebase. Go to VCS/Git/Rebase. Then select Interactive option. It will show you a list of commits, where you can pick which ones you want to squash.
After you hit Start rebasing it will prompt you for a commit message for the squashed commit. After that is done you can push your squashed commit using push dialog.
More information about rebase in IntelliJ is here.