If you are creating your Pearson VUE  account and you have already passed some Oracle certifications earlier, you need to put your old Prometric id so that your old certifications at Prometric get merged automatically with the new Pearson account. But, if you forgot your old Prometric id, as happened to me, you can probably get it by raising SR with Oracle certification team at:

http://education.oracle.com/pls/eval-eddap-dcd/OU_SUPPORT_OCP.home?p_source=OCP .

I got my ID by raising SR at this link, for this, I provided my first name, last name and Date-of-Birth. Oracle did not ask any further questions and replied back with my testing-id   🙂