Hiya
1) Download & Install Microsoft Security Compliance manager
2) Identify relevant Baseline
3) Duplicate a copy (which will allow you to edit only the copy)
4) export the copy as a DCM2007 object *.cab or SCM object *.cab
5) Import into SCCM 2012 as a baseline.
6) you will then be able to see the items you created and the corrresponding baselines.
If these do not fit your requirements then you'll have to adjust them to fit or create your own..
Hope this helps