Branch A has commits (X,Y) that also need to be in Branch B. The cherry-pick operations should be done in the same chronological order that the commits appear in Branch A.
cherry-pick does support a range of commits, but if you have merge commits in that range, it gets really complicated
git checkout branch-B
git cherry-pick X
git cherry-pick Y
Branch A has a series of commits (X..Y) that need to be moved to branch B. For this case, you'll need to specify the commit before the initial commit you're interested in order for it to be included. Example: you want commits B..D from (...A->B->C->D-E->...) you would use "A" as the starting commit. You'll also need the commit SHA for the HEAD of the branch you are transferring to.
git checkout branch-B
git log # Note the SHA of most recent commit (M)
git rebase --onto M <commit before X> Y
git rebase HEAD branch-B