Graphic design courses: What courses and certificates that might help me make the transition from graphic design to UI design?

CSS, ANGULARJS MAY HELP YOU TO CHANGE FROM GRAPHIC TO UI 

see the article

https://blogs.adobe.com/creativecloud/5-tips-for-graphic-designers-switching-to-ux-design/

YouTube site

Contains tutorials

Use a Google site that contains sites offering courses in this area

Practice is better than courses

I think the principles you acquired from graphic design will suffice. But if you feel like a certificate will increase your chances of getting hired I'd say look for classes on mobile design or anything related to small devices. That's so important to be aware of nowadays. A lot of applications and websites today are designed for mobile first. Then, they think of augmenting it to bigger devices. 

KNow the basics of Graphic Designing and more importantly Learn some of the softwares like PhotoShop, CorelDraw and some of the related things. You don't need any certififcation but practice and expertise about the designing visualizations matters alot.

Certificate is nothing, Practices and experience is the great teacher.