AI / ML / DL skill is a blend of programming, data, and business logic.
To build a career in AI / ML, one needs to build a strong foundation in mathematics / statistics. Some of the topics to mention are probability, statistics, linear algebra, mathematical optimisation etc.
One needs to learn algorithms like decision tree, nearest neighbour, neural net, support vector machine, ensemble of multiple models, linear regression, gradient descent, genetic algorithms, bagging, boosting etc.
Popular AI/ML languages include R, Python, Lisp, Prolog and Scala. If one already knows one of these languages, it becomes lot easier.
Typically, for migrating to AI / ML, statistical programmer can be trained in data strategy, or someone skilled in data processing can be taught statistical algorithms.