Go to Linkedin,

(1) Search those who have similar degrees, working patterns, qualifications, job like you.
(2) Look at their career paths - decide which ones meet your expectation for the "senior".
(3) Think why and how they choose their paths.

To be a senior, you need to analyze and draw the conclusion by yourself. This is something you have to learn and pick up the skills indepedently.

However, if you really need a mentor, there are some commercial services. You just need to google the keywords and sign up the programs.