I created a new branch named newbranch from the master branch in git. Now I have done some work and want to merge newbranch to master; however, I have made some extra changes to newbranch and I want to merge newbranch up to the fourth-from-the-last commit to master.

I used cherry-pick but it shows the message to use the right options:

git checkout master    
git cherry-pick ^^^^HEAD newbranch

Can I use git merge to do it instead?

git merge newbranch <commitid>

Sure, being in master branch all you need to do is:

git merge <commit-id>

where commit-id is hash of the last commit from newbranch that you want to get in your master branch.

You can find out more about any git command by doing git help <command>. It that case it's git help merge. And docs are saying that the last argument for merge command is <commit>..., so you can pass reference to any commit or even multiple commits. Though, I never did the latter myself.